drm/panthor: Add GPU register definitions

Those are the registers directly accessible through the MMIO range.

FW registers are exposed in panthor_fw.h.

v6:
- Add Maxime's and Heiko's acks

v4:
- Add the CORE_FEATURES register (needed for GPU variants)
- Add Steve's R-b

v3:
- Add macros to extract GPU ID info
- Formatting changes
- Remove AS_TRANSCFG_ADRMODE_LEGACY - it doesn't exist post-CSF
- Remove CSF_GPU_LATEST_FLUSH_ID_DEFAULT
- Add GPU_L2_FEATURES_LINE_SIZE for extracting the GPU cache line size

Co-developed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Steven Price <steven.price@arm.com> # MIT+GPL2 relicensing,Arm
Acked-by: Grant Likely <grant.likely@linaro.org> # MIT+GPL2 relicensing,Linaro
Acked-by: Boris Brezillon <boris.brezillon@collabora.com> # MIT+GPL2 relicensing,Collabora
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240229162230.2634044-3-boris.brezillon@collabora.com