drm/i915/buddy: add some pretty printing

Implement the debug hook for the buddy resource manager. For this we
want to print out the status of the memory manager, including how much
memory is still allocatable, what page sizes we have etc. This will be
triggered when TTM is unable to fulfil an allocation request for device
local-memory.

v2(Thomas):
    - s/MB/MiB
    - s/KB/KiB

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210819093419.295636-1-matthew.auld@intel.com