Add protocol specific operation for CIFS xattrs

Changeset 666753c3 added protocol
operations for get/setxattr to avoid calling cifs operations
on smb2/smb3 mounts for xattr operations and this changeset
adds the calls to cifs specific protocol operations for xattrs
(in order to reenable cifs support for xattrs which was
temporarily disabled by the previous changeset.  We do not
have SMB2/SMB3 worker function for setting xattrs yet so
this only enables it for cifs.

CCing stable since without these two small changsets (its
small coreq 666753c3 is
also needed) calling getfattr/setfattr on smb2/smb3 mounts
causes problems.

Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Shirish Pargaonkar <spargaonkar@suse.com>
CC: Stable <stable@kernel.org>