backing-dev: kill unused pdflush_proc_obsolete()

After commit b35bd0d9f8a8, pdflush_proc_obsolete() is no longer
used. Kill the function and declaration.

Reported-by: Rakesh Pandit <rakesh@tuxera.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2 files changed