BACKPORT: f2fs: support RO feature

Given RO feature in superblock, we don't need to check provisioning/reserve
spaces and SSA area.

Bug: 208371174
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 60bad8157831)
Change-Id: I2ec5fda15948bb17bd34b3b1c3efc356f527b515