drm/selftests: add drm buddy optimistic testcase

drm/selftests: add drm buddy optimistic testcase

create a mm with one block of each order available, and
try to allocate them all.

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/20220222174845.2175-4-Arunpravin.PaneerSelvam@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>