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>

arch/mips/loongson/common/platform.c

@@ -9,6 +9,7 @@
  */
 
 #include <linux/err.h>
+#include <linux/smp.h>
 #include <linux/platform_device.h>
 
 static struct platform_device loongson2_cpufreq_device = {

arch/mips/vr41xx/common/giu.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>
 

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>