UBIFS: call dbg_is_power_cut() instead of reading c->dbg->pc_happened

Call dbg_is_power_cut() to emulate power cut instead of reading
c->dbg->pc_happened. Otherwise, the function becomes dead code.

CRs-Fixed: 975289
Change-Id: Ib900fad109c1481b2524988ba50a872af36ac6a8
Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Git-commit: 8f6983abe31f37d953197c3ede14b1d1321affee
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


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