mm/zswap.c: remove unused function zswap_debugfs_exit()

mm/zswap.c: remove unused function zswap_debugfs_exit()

Patch series "Cleanup and fixup for zswap".

This series contains cleanups to remove unused function and avoid
unnecessary copy-in at map time.  Also this fixes two bugs in the function
zswap_writeback_entry().  More details can be found in the respective
changelogs.

This patch (of 3):

zswap_debugfs_exit() is unused, remove it.

Link: https://lkml.kernel.org/r/20210522092242.3233191-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210522092242.3233191-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>