powerpc: Fix up implicit stat.h users

They get it via module.h (via device.h) but we want to clean that up.
When we do, we'll get things like:

ibmebus.c:314: error: 'S_IWUSR' undeclared here (not in a function)
vio.c:972: error: 'S_IWUSR' undeclared here (not in a function)

so add in the stat header it is using explicitly in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/powerpc/kernel/vio.c b/arch/powerpc/kernel/vio.c
index 1b695fd..ee09398 100644
--- a/arch/powerpc/kernel/vio.c
+++ b/arch/powerpc/kernel/vio.c
@@ -15,6 +15,7 @@
  */
 
 #include <linux/types.h>
+#include <linux/stat.h>
 #include <linux/device.h>
 #include <linux/init.h>
 #include <linux/slab.h>