mips: fix implicit smp.h usage in various files.

We need to call out inclusion of smp.h, or with the module.h cleanup
we'll get things like:

arch/mips/loongson/common/platform.c:21: error: implicit declaration of function 'smp_processor_id'

arch/mips/vr41xx/common/giu.c:84: error: implicit declaration of function 'smp_processor_id'

arch/mips/vr41xx/common/rtc.c:85: error: implicit declaration of function 'smp_processor_id'

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/mips/vr41xx/common/rtc.c b/arch/mips/vr41xx/common/rtc.c
index ebc5dcf..76e3e8a 100644
--- a/arch/mips/vr41xx/common/rtc.c
+++ b/arch/mips/vr41xx/common/rtc.c
@@ -19,6 +19,7 @@
  */
 #include <linux/errno.h>
 #include <linux/init.h>
+#include <linux/smp.h>
 #include <linux/ioport.h>
 #include <linux/platform_device.h>