dm9000: avoid sleeping in dm9000_timeout callback

On the DM9000B, dm9000_msleep() is called during the dm9000_timeout()
routine.  Since dm9000_timeout() holds the main spinlock through the
entire routine, mdelay() needs to be used rather than msleep().
Furthermore, the mutex_lock()/mutex_unlock() should be avoided so as to
not sleep with spinlocks held.

Signed-off-by: Andrew Ruder <andrew.ruder@elecsyscorp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>