dynamic_debug: Add __dynamic_dev_dbg

Unlike dynamic_pr_debug, dynamic uses of dev_dbg can not
currently add task_pid/KBUILD_MODNAME/__func__/__LINE__
to selected debug output.

Add a new function similar to dynamic_pr_debug to
optionally emit these prefixes.

Cc: Aloisio Almeida <aloisio.almeida@openbossa.org>
Noticed-by: Aloisio Almeida <aloisio.almeida@openbossa.org>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/linux/device.h b/include/linux/device.h
index c20dfbf..4639419 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -785,6 +785,8 @@
 
 #ifdef CONFIG_PRINTK
 
+extern int __dev_printk(const char *level, const struct device *dev,
+			struct va_format *vaf);
 extern int dev_printk(const char *level, const struct device *dev,
 		      const char *fmt, ...)
 	__attribute__ ((format (printf, 3, 4)));
@@ -805,6 +807,9 @@
 
 #else
 
+static inline int __dev_printk(const char *level, const struct device *dev,
+			       struct va_format *vaf)
+	 { return 0; }
 static inline int dev_printk(const char *level, const struct device *dev,
 		      const char *fmt, ...)
 	__attribute__ ((format (printf, 3, 4)));