[BNX2]: Add delay before reading firmware version.

The management firmware may still be loading during bnx2_init_one()
because of the D3hot -> D0 transition and the firmware version may
not be available without waiting a bit.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>