platforms/xgene: Make use of dt_device_get_address return value

Currently function xgene_check_pirq_eoi assigns the return value of
dt_device_get_address to a variable res but does not make use of it.
Fix it by making use of res in the condition checking the result of a
call to dt_device_get_address instead of checking the address stored in
dbase.

Signed-off-by: Michal Orzel <michal.orzel@arm.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

xen/arch/arm/platforms/xgene-storm.c

@@ -51,7 +51,7 @@ static void __init xgene_check_pirq_eoi(void)
         panic("%s: Can not find interrupt controller node\n", __func__);
 
     res = dt_device_get_address(node, 0, &dbase, NULL);
-    if ( !dbase )
+    if ( res )
         panic("%s: Cannot find a valid address for the distributor\n", __func__);
 
     /*