drm/selftests: add drm buddy pathological testcase

create a pot-sized mm, then allocate one of each possible
order within. This should leave the mm with exactly one
page left. Free the largest block, then whittle down again.
Eventually we will have a fully 50% fragmented mm.

v2(Matthew Auld):
  - removed unnecessary test succeeded print
  - replace list_del()/list_add_tail() with list_move_tail()

Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220222174845.2175-7-Arunpravin.PaneerSelvam@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>