Similar to blkdev_write_iter(), return -EPERM if the partition is
read-only.  This covers ioctl(), fallocate() and most in-kernel users
but isn't meant to be exhaustive -- everything else will be caught in
generic_make_request_checks(), fail with -EIO and can be fixed later.
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>