gianfar: Fix error in mdio reset timeout

gianfar: Fix error in mdio reset timeout

The loop with the timeout used "while (...  && timeout--)", which means
than when the timeout occurs, "timeout" will be -1 after the loop has
exited.  The code that checks if the looped exited because of a timeout
used "if (timeout <= 0)".  Seems ok, except timeout is unsigned, and
(unsigned)-1 isn't less than zero!

Using "--timeout" in the loop fixes this problem, as now "timeout" will be
0 when the loop times out.

This also fixes a bug in the existing code, where it will erroneously think
a timeout occurred if the condition the loop was waiting for is satisfied
on the final iteration before a timeout.

Signed-off-by: Trent Piepho <tpiepho@freescale.com>
Acked-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>