drm: Remove DRM_ARRAY_SIZE() for ARRAY_SIZE()

I cannot see a need to provide a DRM_ version of ARRAY_SIZE(), only used
in a few places. I suspect its usage has been spread by copy & paste
rather than anything else.

Let's just remove it for plain ARRAY_SIZE().

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>