Replace the usage of per-quota region priorities histogram buffer with the
per-context one.  After this change, the per-quota histogram is not used
by anyone, and hence it is ready to be removed.

Link: https://lkml.kernel.org/r/20240826042323.87025-3-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>