drm: enable almost all PCIe functionality

linux_pci.c revisions 1.24 and 1.25 implemented most of the remaining
missing PCIe backends, but only enabled them for some amdgpu portions.

this enables all code marked with "XXX amdgpu pcie", "XXX radeon pcie",
and "XXX pcie speed". for most of it, simply removing #ifndefs __NetBSD__
to enable compliation was required, once the new "bus->max_bus_speed"
member was added to struct pci_bus. add an "always fails" backend for
pci_enable_atomic_ops_to_root() which seems to only be necessary
for virtual GPU functionality (and could be implemented if needed.)

tested on radeon 5450, 7750, R7 240 [radeon], and RX 550 [amdgpu], and
nvidia 750 and 1030 [nouveau].


this still does not quite work on nvidia cards. there are two problems
that remain:

- the call to set the link speed is skipped because the speed is set
to the default value of "-1". nvkm_pcie_set_link() will actually
determine the right value for this and for some cards, calling this
function if the current speed is -1 helps set the link speed. it
may be that on linux other paths we don't have enabled properly
would set this (there's one via debugfs, and a jetson specific one,
though perhaps setting either AC or DC speed values as boot options
(after hooking up these for netbsd) would currently work.

- worse, cards newer than kepler - geforce 900, 1000, and newer, are
all lacking the backing support to set pcie link speed. the GT 1030
card i have been testing with remains at pcie 1.0.

amdgpu: Another pass through.

amdgpu_object.c
amdgpu_pci.c
amdgpu_pm.c
amdgpu_polaris10_smumgr.c
amdgpu_pp_psm.c
amdgpu_ppatomctrl.c
amdgpu_ppatomfwctrl.c
amdgpu_process_pptables_v1_0.o
amdgpu_psp.o
amdgpu_psp_v10_0.c
amdgpu_psp_v11_0.c
amdgpu_psp_v12_0.c
amdgpu_psp_v3_1.c
amdgpu_ras.c
amdgpu_ras_eeprom.c
amdgpu_rc_calc.c
amdgpu_rc_calc_dpi.c
amdgpu_ring.c
amdgpu_rlc.c
amdgpu_rn_clk_mgr.c
amdgpu_sdma_v3_0.c
amdgpu_sdma_v4_0.c
amdgpu_sdma_v5_0.c
amdgpu_si.c
amdgpu_si_dma.c
amdgpu_si_dpm.c
amdgpu_smu.c
amdgpu_smu10_hwmgr.c
amdgpu_smu7_hwmgr.c
amdgpu_smu8_hwmgr.c
amdgpu_smu8_smumgr.c
amdgpu_smu_v11_0.c (and a sprinkling of consts)
amdgpu_smu_v11_0_i2c.c
amdgpu_soc15.c
amdgpu_tonga_smumgr.c
amdgpu_ttm.c
amdgpu_ucode.c
amdgpu_uvd.c
amdgpu_uvd_v5_0.c
amdgpu_uvd_v6_0.c
amdgpu_uvd_v7_0.c
amdgpu_vce.c
amdgpu_vce_v2_0.c
amdgpu_vce_v4_0.c
amdgpu_vcn_v1_0.c
amdgpu_vcn_v2_0.c
amdgpu_vcn_v2_5.c
amdgpu_vega10_hwmgr.c
amdgpu_vega10_powertune.c
amdgpu_vega10_processpptables.c
amdgpu_vega10_reg_init.c
amdgpu_vega12_hwmgr.c
amdgpu_vega20_hwmgr.c
amdgpu_vega20_ppt.c
amdgpu_vega20_reg_init.c
amdgpu_vi.c
amdgpu_virt.c
amdgpu_vram_mgr.c
amdgpu_xgmi.c -- disable (for now?)
amdgpufb.c

Merge linux-drm-v5-6-rc3

branches: 1.1.1; 1.1.2; 1.1.6;
Rename amdgpu files to avoid clashes with radeon.

amdgpu: Another pass through.

amdgpu_object.c
amdgpu_pci.c
amdgpu_pm.c
amdgpu_polaris10_smumgr.c
amdgpu_pp_psm.c
amdgpu_ppatomctrl.c
amdgpu_ppatomfwctrl.c
amdgpu_process_pptables_v1_0.o
amdgpu_psp.o
amdgpu_psp_v10_0.c
amdgpu_psp_v11_0.c
amdgpu_psp_v12_0.c
amdgpu_psp_v3_1.c
amdgpu_ras.c
amdgpu_ras_eeprom.c
amdgpu_rc_calc.c
amdgpu_rc_calc_dpi.c
amdgpu_ring.c
amdgpu_rlc.c
amdgpu_rn_clk_mgr.c
amdgpu_sdma_v3_0.c
amdgpu_sdma_v4_0.c
amdgpu_sdma_v5_0.c
amdgpu_si.c
amdgpu_si_dma.c
amdgpu_si_dpm.c
amdgpu_smu.c
amdgpu_smu10_hwmgr.c
amdgpu_smu7_hwmgr.c
amdgpu_smu8_hwmgr.c
amdgpu_smu8_smumgr.c
amdgpu_smu_v11_0.c (and a sprinkling of consts)
amdgpu_smu_v11_0_i2c.c
amdgpu_soc15.c
amdgpu_tonga_smumgr.c
amdgpu_ttm.c
amdgpu_ucode.c
amdgpu_uvd.c
amdgpu_uvd_v5_0.c
amdgpu_uvd_v6_0.c
amdgpu_uvd_v7_0.c
amdgpu_vce.c
amdgpu_vce_v2_0.c
amdgpu_vce_v4_0.c
amdgpu_vcn_v1_0.c
amdgpu_vcn_v2_0.c
amdgpu_vcn_v2_5.c
amdgpu_vega10_hwmgr.c
amdgpu_vega10_powertune.c
amdgpu_vega10_processpptables.c
amdgpu_vega10_reg_init.c
amdgpu_vega12_hwmgr.c
amdgpu_vega20_hwmgr.c
amdgpu_vega20_ppt.c
amdgpu_vega20_reg_init.c
amdgpu_vi.c
amdgpu_virt.c
amdgpu_vram_mgr.c
amdgpu_xgmi.c -- disable (for now?)
amdgpufb.c

Merge linux-drm-v5-6-rc3

branches: 1.1.1; 1.1.2; 1.1.6;
Rename amdgpu files to avoid clashes with radeon.

branches: 1.1.2;
Rename amdgpu files to avoid clashes with radeon.