xen: Add __attribute__((format(printf... where appropriate

Use the compiler to verify printf formats and arguments.

Fix fallout.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/include/xen/hvc-console.h b/include/xen/hvc-console.h
index c3adde3..901724d 100644
--- a/include/xen/hvc-console.h
+++ b/include/xen/hvc-console.h
@@ -6,11 +6,13 @@
 #ifdef CONFIG_HVC_XEN
 void xen_console_resume(void);
 void xen_raw_console_write(const char *str);
+__attribute__((format(printf, 1, 2)))
 void xen_raw_printk(const char *fmt, ...);
 #else
 static inline void xen_console_resume(void) { }
 static inline void xen_raw_console_write(const char *str) { }
-static inline void xen_raw_printk(const char *fmt, ...) { }
+static inline __attribute__((format(printf, 1, 2)))
+void xen_raw_printk(const char *fmt, ...) { }
 #endif
 
 #endif	/* XEN_HVC_CONSOLE_H */