xfs: XFS_ONLINE_SCRUB_STATS should depend on DEBUG_FS

Currently, XFS_ONLINE_SCRUB_STATS selects DEBUG_FS.  However, DEBUG_FS
is meant for debugging, and people may want to disable it on production
systems.  Since commit 0ff51a1f ("xfs: enable online fsck by
default in Kconfig")), XFS_ONLINE_SCRUB_STATS is enabled by default,
forcing DEBUG_FS enabled too.

Fix this by replacing the selection of DEBUG_FS by a dependency on
DEBUG_FS, which is what most other options controlling the gathering and
exposing of statistics do.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>