drm/i915: Move the size computations to drm buddy

drm/i915: Move the size computations to drm buddy

- Move roundup_power_of_two() to drm buddy file to support
  the new try harder mechanism for contiguous allocation.

- Move trim function call to drm_buddy_alloc_blocks() function.

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230909160902.15644-2-Arunpravin.PaneerSelvam@amd.com
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Christian König <christian.koenig@amd.com>