printk: Add a DEPRECATED macro

sctp has several points in its setsockopt path in which it issues deprecation
warnings.  It seems like it might be handy to macrotize such a warning so other
subsystems can use it easily

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: "David S. Miller" <davem@davemloft.net>
CC: linux-kernel@vger.kernel.org
CC: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/printk.h

@@ -87,6 +87,13 @@ struct va_format {
  */
 #define HW_ERR		"[Hardware Error]: "
 
+/*
+ * DEPRECATED
+ * Add this to a message whenever you want to warn user space about the use
+ * of a deprecated aspect of an API so they can stop using it
+ */
+#define DEPRECATED	"[Deprecated]: "
+
 /*
  * Dummy printk for disabled debugging statements to use whilst maintaining
  * gcc's format and side-effect checking.