bna: Clear Driver Config Flags When HW Resets

Driver configuration flags are retained across open/stop operations preventing
configurations to be set in next open/stop. Setting MTU on a 1020 causes
network to fail until a reboot is performed on the host.

Clear the flags when configuration resets in hardware.

Signed-off-by: Rasesh Mody <rmody@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>