Revert "drm/amdgpu: validate user GEM object size"

It was at the same time too strict (for linear tiling modes, where no
height alignment is required) and too lenient (for 2D tiling modes,
where height may need to be aligned to values > 8).

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>