ext4: convert to new fserror helpers

ext4: convert to new fserror helpers

Use the new fserror functions to report metadata errors to fsnotify.
Note that ext4 inconsistently passes around negative and positive error
numbers all over the codebase, so we force them all to negative for
consistency in what we report to fserror, and fserror ensures that only
positive error numbers are passed to fanotify, per the fanotify(7)
manpage.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://patch.msgid.link/176826402693.3490369.5875002879192895558.stgit@frogsfrogsfrogs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>