Most devices expose at least the link up/down status via a bit in a
MAC register, since the MAC generally already needs to know whether or
not the link is up.  Some devices (e.g. the SMSC75xx USB NIC) expose
this information to software only via the MII registers.

Provide a generic mii_check_link() implementation to check the BMSR
and report the link status via netdev_link_{up,down}().

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Relicense files for which I am the sole author (as identified by
util/relicense.pl).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>

iPXE provides no support for manually configuring the link speed.
Provide a generic routine which should be able to reset any MII/GMII
PHY and enable autonegotiation.

Prototyped-by: Thomas Miletich <thomas.miletich@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>