drm/amdgpu: add asic callback for querying video codec info (v3)

This will be used by a new INFO ioctl query to fetch the decode
and encode capabilities from the kernel driver rather than
hardcoding them in mesa.  This gives us more fine grained control
of capabilities using information that is only availabl in the
kernel (e.g., platform limitations or bandwidth restrictions).

v2: reorder the codecs to better align with mesa
v3: add max_pixels_per_frame to handle the portrait case

Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com> (v2)
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>