USB: mcs7830: return negative if auto negotiate fails

The original code returns 0 on success and 1 on failure.  In fact, at
this point, "ret" is already either zero or a negative error code so
we can just return it directly.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>