drm/tests/drm_buddy: fix 32b build

drm/tests/drm_buddy: fix 32b build

Doesn't seem to compile on 32b, presumably due to u64 mod/division.
Simplest is to just switch over to u32 here. Also make print modifiers
consistent with that.

Fixes: a64056bb5a32 ("drm/tests/drm_buddy: add alloc_contiguous test")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Maxime Ripard <mripard@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240215174431.285069-7-matthew.auld@intel.com
Signed-off-by: Christian König <christian.koenig@amd.com>