powerpc: use machine_subsys_initcall() for opal_hmi_handler_init()

As opal_message_init() uses machine_early_initcall(powernv, ), and
opal_hmi_handler_init() depends on that early initcall, so it also needs
use machine_* to check the machine_id.
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>

arch/powerpc/platforms/powernv/opal-hmi.c

@@ -28,6 +28,7 @@
 
 #include <asm/opal.h>
 #include <asm/cputable.h>
+#include <asm/machdep.h>
 
 static int opal_hmi_handler_nb_init;
 struct OpalHmiEvtNode {
@@ -185,4 +186,4 @@ static int __init opal_hmi_handler_init(void)
 	}
 	return 0;
 }
-subsys_initcall(opal_hmi_handler_init);
+machine_subsys_initcall(powernv, opal_hmi_handler_init);