UBIFS: Add security.* XATTR support for the UBIFS

Artem: rename static functions so that they do not use the "ubifs_" prefix - we
       only use this prefix for non-static functions.
Artem: remove few junk white-space changes in file.c

Signed-off-by: Subodh Nijsure <snijsure@grid-net.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Ben Shelton <ben.shelton@ni.com>
Acked-by: Brad Mouring <brad.mouring@ni.com>
Acked-by: Terry Wilcox <terry.wilcox@ni.com>
Acked-by: Gratian Crisan <gratian.crisan@ni.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>