Fix PHY Lib support for gianfar and ucc_geth

The PHY Lib now uses mutexes instead of spin_locks.  ucc_geth
and gianfar both grab the locks in their mdio_reset functions,
so they need to use mutex_(un)lock instead.  This was not caught
until someone tested it on an SMP system.

Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>