drm/amdgpu: Add support for querying the max ibs in a submission. (v3)

drm/amdgpu: Add support for querying the max ibs in a submission. (v3)

This info would be used by radv to figure out when we need to
split a submission into multiple submissions. radv currently has
a limit of 192 which seems to work for most gfx submissions, but
is way too high for e.g. compute or sdma.

Userspace is available at
https://gitlab.freedesktop.org/bnieuwenhuizen/mesa/-/commits/ib-rejection-v3

v3: Completely rewrote based on suggestion of making it a separate query.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2498
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>