bnx2x: fix a crash on corrupt firmware file

If the requested firmware is deemed corrupt and then released, reset the
pointer to NULL in order to avoid double-freeing it in
bnx2x_release_firmware() or dereferencing it in bnx2x_init_firmware().
Signed-off-by: NMichal Schmidt <mschmidt@redhat.com>
Acked-by: NEilon Greenstein <eilong@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c

@@ -10901,6 +10901,7 @@ int bnx2x_init_firmware(struct bnx2x *bp)
 	kfree(bp->init_data);
 request_firmware_exit:
 	release_firmware(bp->firmware);
+	bp->firmware = NULL;
 
 	return rc;
 }