drm: drm_printer: add __printf validation

drm_printf does not currently use the compiler to verify
format and arguments.  Make it do so.

Miscellanea:

o Add appropriate #include files for __printf and struct va_format
o Convert dev_printk to dev_info
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/133858f214e9b90f92bb8eb44c6b1dc04429933d.1487201526.git.joe@perches.com

drivers/gpu/drm/drm_print.c

@@ -36,7 +36,7 @@ EXPORT_SYMBOL(__drm_printfn_seq_file);
 
 void __drm_printfn_info(struct drm_printer *p, struct va_format *vaf)
 {
-	dev_printk(KERN_INFO, p->arg, "[" DRM_NAME "] %pV", vaf);
+	dev_info(p->arg, "[" DRM_NAME "] %pV", vaf);
 }
 EXPORT_SYMBOL(__drm_printfn_info);
 

include/drm/drm_print.h

@@ -26,6 +26,8 @@
 #ifndef DRM_PRINT_H_
 #define DRM_PRINT_H_
 
+#include <linux/compiler.h>
+#include <linux/printk.h>
 #include <linux/seq_file.h>
 #include <linux/device.h>
 
@@ -75,6 +77,7 @@ void __drm_printfn_seq_file(struct drm_printer *p, struct va_format *vaf);
 void __drm_printfn_info(struct drm_printer *p, struct va_format *vaf);
 void __drm_printfn_debug(struct drm_printer *p, struct va_format *vaf);
 
+__printf(2, 3)
 void drm_printf(struct drm_printer *p, const char *f, ...);