UBIFS: fix checkpatch.pl warnings

These are mostly long lines and wrong indentation warning
fixes. But also there are two volatile variables and
checkpatch.pl complains about them:

WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
+       volatile int gc_seq;

WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
+       volatile int gced_lnum;

Well, we anyway use smp_wmb() for c->gc_seq and c->gced_lnum, so
these 'volatile' modifiers can be just dropped.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>