drm/tests/buddy: fix print format

drm/tests/buddy: fix print format

This will report a build warning once we have: 806cb2270237 ("kunit:
Annotate _MSG assertion variants with gnu printf specifiers").

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: c70703320e55 ("drm/tests/drm_buddy: add alloc_range_bias test")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Reviewed-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Link: https://lore.kernel.org/r/20240229095225.242795-2-matthew.auld@intel.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>