drm/tests: Add a test case for drm buddy clear allocation

drm/tests: Add a test case for drm buddy clear allocation

Add a new test case for the drm buddy clear and dirty
allocation.

v2:(Matthew)
  - make size as u32
  - rename PAGE_SIZE with SZ_4K
  - dont fragment the address space for all the order allocation
    iterations. we can do it once and just increment and allocate
    the size.
  - create new mm with non power-of-two size to ensure the multi-root
    force_merge during fini.

v3:
  - add randomness in size calculation(Matthew)

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Suggested-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419063538.11957-3-Arunpravin.PaneerSelvam@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>