net:cpsw: Pass unhandled ioctl's on to generic phy ioctl

This patch allows the use of a generic timestamping phy connected
to the cpsw if CPTS support is not enabled. This also adds support
of the SIOCGMIIREG and SIOCSMIIREG, and moves handling of SIOCGMIIPHY
to the generic driver.

Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>