UBIFS: add ubifs_err() to print error reason

This patch adds ubifs_err() output to some error paths to tell the user
what's going on.

Artem: improve the messages, rename too long variable

Change-Id: Ib6ed7a8696bf1a18fc6d11389406621193ac8219
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>
Git-commit: fee1756d80c24d5a3171cb9f76d612e512439dd2
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>