[qib7322] Fix compiler warning on gcc 4.7

Originally-fixed-by: Christian Hesse <list@eworm.de>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/infiniband/qib7322.c

 	struct QIB_7322_ahb_transaction_reg xact;
 	int rc;
 
+	/* Avoid returning uninitialised data on error */
+	*data = 0;
+
 	/* Initiate transaction */
 	memset ( &xact, 0, sizeof ( xact ) );
 	BIT_FILL_2 ( &xact,