drm/amd/display: dc/irq: add support for DCE6 (v4)

[Why]
irq service requires changes for DCE6 support

[How]
(v1) DCE6 targets are added replicating existing DCE8 implementation.
due to missing CRTC_VERTICAL_INTERRUPT0_CONTROL registers/masks,
dce/dce_8_0_{d,sh_mask}.h used instead of dce/dce_6_0_{d,sh_mask}.h

(v2) DCE6 headers used adding the necessary vblank irq registers
(INT_MASK and VBLANK_STATUS) and vblank irq masks as implemented
in amdgpu driver.
Add vblank_irq_info_funcs_dce60 with .set and .ack as per commit
b10d51f ("drm/amd/display: Add interrupt entries for VBLANK isr.")
and use it in vblank_int_entry(reg_num) macro definition

(v3) updated due to following kernel 5.3 commit:
4fc4dca ("drm/amd: drop use of drmp.h in os_types.h")

(v4) updated due to following kernel 5.6 commit:
d9e3267 ("drm/amd/display: cleanup of construct and destruct funcs")

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>