The buffer size is 2 Bytes and we expect to receive the same amount of
data. But sometimes we receive less data and run into uninit-was-stored
issue upon read. Hence modify the error check on the return value to match
with the buffer size as a prevention.

Reported-and-tested by: syzbot+a7e220df5a81d1ab400e@syzkaller.appspotmail.com
Signed-off-by: Himadri Pandya <himadrispandya@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>