gfs2: Add wrapper for iomap_file_buffered_write

gfs2: Add wrapper for iomap_file_buffered_write

BugLink: https://bugs.launchpad.net/bugs/1976135
commit 2eb7509a05443048fb4df60b782de3f03c6c298b upstream

Add a wrapper around iomap_file_buffered_write.  We'll add code for when
the operation needs to be retried here later.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>