mdio: mdio_if_info::mmds should not be __bitwise

I misunderstood the meaning of __bitwise.  In practice it makes sparse
warn about every use of mmds which is certainly not what we want.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>