platform/mihawk: Detect old system compatible string

Newer firmware declares the system as "ibm,mihawk", but the labs are
full of older installs, which were using "wistron,mihawk". Let's keep
detecting the older string since it allows to run recent skiboot on
older fw stack and make people's lives a little tiny bit easier.

Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Stewart Smith <stewart@flamingspork.com>
Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

platforms/astbmc/mihawk.c

@@ -231,7 +231,8 @@ static void mihawk_create_ocapi_i2c_bus(void)
 
 static bool mihawk_probe(void)
 {
-	if (!dt_node_is_compatible(dt_root, "ibm,mihawk"))
+	if (!dt_node_is_compatible(dt_root, "ibm,mihawk") &&
+	    !dt_node_is_compatible(dt_root, "wistron,mihawk"))
 		return false;
 
 	/* Lot of common early inits here */