B44: increase wait loop

The b44 Enet control disable bit may take longer to clear on some
systems, so the loop count is increased with this patch. Functionality
is not compromised, but a debug message can be seen when the bit is not
cleared within the count value.
Thanks to Vasileios Lourdas who reported the problem.

Signed-off by: Gary Zambrano <zambrano@broadcom.com>

Signed-off-by: Jeff Garzik <jeff@garzik.org>