DM9000: Do not sleep with spinlock and IRQs held

The phy read and write routines call udelay() with the board
lock held, and with the posibility of IRQs being disabled. Since
these delays can be up to 500usec, and are only required as we
have to save the chip's address register.

To improve the behaviour, hold the lock whilst we are writing
and then restore the state before the delay and then repeat
the process once the delay has happened.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>