of: add 'of_' prefix to machine_is_compatible()

machine is compatible is an OF-specific call.  It should have
the of_ prefix to protect the global namespace.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Michal Simek <monstr@monstr.eu>
diff --git a/drivers/serial/pmac_zilog.c b/drivers/serial/pmac_zilog.c
index 683e66f..3e2ae48 100644
--- a/drivers/serial/pmac_zilog.c
+++ b/drivers/serial/pmac_zilog.c
@@ -2031,9 +2031,9 @@
 	/*
 	 * XServe's default to 57600 bps
 	 */
-	if (machine_is_compatible("RackMac1,1")
-	    || machine_is_compatible("RackMac1,2")
-	    || machine_is_compatible("MacRISC4"))
+	if (of_machine_is_compatible("RackMac1,1")
+	    || of_machine_is_compatible("RackMac1,2")
+	    || of_machine_is_compatible("MacRISC4"))
 	 	baud = 57600;
 
 	/*