drm/i915/buddy: sanity check the size

Ensure we check that the size is compatible with the requested
page_size. For tiny objects that are automatically annotated with
TTM_PL_FLAG_CONTIGUOUS(since they fit within a single page), we
currently end up silently overriding the min_page_size, which ends up
hiding bugs elsewhere.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Nirmoy Das <nirmoy.das@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220420181613.70033-2-matthew.auld@intel.com