drm/xe: Modify the cfb size to be page size aligned for FBC

drm_gem_private_object_init expect the object size be page size
aligned. The xe_bo create functions do not update the size for
any alignment requirements. So align cfb size to be page size
aligned in xe stolen memory handling.

Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240112092803.61664-2-vinod.govindapillai@intel.com