bcache: fix mistaken sysfs entry for io_error counter

bcache: fix mistaken sysfs entry for io_error counter

BugLink: https://bugs.launchpad.net/bugs/1839036
commit 5461999848e0462c14f306a62923d22de820a59c upstream.

In bch_cached_dev_files[] from driver/md/bcache/sysfs.c, sysfs_errors is
incorrectly inserted in. The correct entry should be sysfs_io_errors.

This patch fixes the problem and now I/O errors of cached device can be
read from /sys/block/bcache<N>/bcache/io_errors.

Fixes: c7b7bd07404c5 ("bcache: add io_disable to struct cached_dev")
Signed-off-by: Coly Li <colyli@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>