f2fs: avoid selinux denial on CAP_SYS_RESOURCE

This fixes CAP_SYS_RESOURCE denial of selinux when using resgid, since it
seems selinux reports it at the first place, but mostly we don't need to
check this condition first.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>