ARM: shmobile: fix smp build

I got build errors with the new version now because machine_is_kzm9g is no longer
defined:

arch/arm/mach-shmobile/platsmp.c: In function 'shmobile_smp_get_core_count':
arch/arm/mach-shmobile/platsmp.c:29:2: error: implicit declaration of function 'of_machine_is_compatible'

Replace the missing function with a call to of_machine_is_compatible.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Acked-by: Magnus Damm <magnus.damm@gmail.com>
diff --git a/arch/arm/boot/dts/sh73a0-kzm9g.dts b/arch/arm/boot/dts/sh73a0-kzm9g.dts
index ed1bae5..bcb9119 100644
--- a/arch/arm/boot/dts/sh73a0-kzm9g.dts
+++ b/arch/arm/boot/dts/sh73a0-kzm9g.dts
@@ -13,7 +13,7 @@
 
 / {
 	model = "KZM-A9-GT";
-	compatible = "renesas,kzm9g";
+	compatible = "renesas,kzm9g", "renesas,sh73a0";
 
 	memory {
 		device_type = "memory";