phy/marvell: Make non-aneg speed/duplex forcing work for 88E1111 PHYs

According to specs, when auto-negotiation is disabled, Marvell PHYs need
a software reset after changing speed/duplex forcing bits. Otherwise,
the modified bits have no effect.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>