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/macintosh/via-pmu-backlight.c b/drivers/macintosh/via-pmu-backlight.c
index a348bb0..4f3c447 100644
--- a/drivers/macintosh/via-pmu-backlight.c
+++ b/drivers/macintosh/via-pmu-backlight.c
@@ -150,13 +150,13 @@
 
 	/* Special case for the old PowerBook since I can't test on it */
 	autosave =
-		machine_is_compatible("AAPL,3400/2400") ||
-		machine_is_compatible("AAPL,3500");
+		of_machine_is_compatible("AAPL,3400/2400") ||
+		of_machine_is_compatible("AAPL,3500");
 
 	if (!autosave &&
 	    !pmac_has_backlight_type("pmu") &&
-	    !machine_is_compatible("AAPL,PowerBook1998") &&
-	    !machine_is_compatible("PowerBook1,1"))
+	    !of_machine_is_compatible("AAPL,PowerBook1998") &&
+	    !of_machine_is_compatible("PowerBook1,1"))
 		return;
 
 	snprintf(name, sizeof(name), "pmubl");