f2fs: fix wrong checkpoint_changed value in f2fs_remount()

f2fs: fix wrong checkpoint_changed value in f2fs_remount()

In f2fs_remount(), return value of test_opt() is an unsigned int type
variable, however when we compare it to a bool type variable, it cause
wrong result, fix it.

Fixes: 4354994f097d ("f2fs: checkpoint disabling")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
[dwoo08.lee: backport from mainline commit 277afbde6ca2]
Signed-off-by: Dongwoo Lee <dwoo08.lee@samsung.com>
Change-Id: Icd4dfff441bf84f605d8d09de7be89da88548654