LU-12511 llite: use mapping_set_error instead of opencoded set_bit

LU-12511 llite: use mapping_set_error instead of opencoded set_bit

The mapping_set_error() helper sets the correct AS_ flag for the mapping
so there is no reason to open code it.  Use the helper directly.

[akpm@linux-foundation.org: be honest about conversion from -ENXIO to -EIO]
Link: http://lkml.kernel.org/r/20160912111608.2588-2-mhocko@kernel.org
Linux-commit: 5114a97a8bce7f4ead29a32b67dee85438699b9e

Lustre-change: https://review.whamcloud.com/51372
Lustre-commit: aac625055e50e83d7716bdfc6ecfab3282eb0ad2

Change-Id: I153bc04d4745a20013820ba81572cadb37ab8f39
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51372
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55553
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>