sony-laptop: add AVMode key mapping

Some models are equipped with an "AVMode" function key that sends
  sony-laptop: Unknown event: 0x100 0xa1
  sony-laptop: Unknown event: 0x100 0x21
for press and release respectively.

Cc: "Matthew W. S. Bell" <matthew@bells23.org.uk>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/include/linux/sonypi.h b/include/linux/sonypi.h
index 34c4475..4f95c1a 100644
--- a/include/linux/sonypi.h
+++ b/include/linux/sonypi.h
@@ -111,6 +111,7 @@
 #define SONYPI_EVENT_VOLUME_INC_PRESSED		69
 #define SONYPI_EVENT_VOLUME_DEC_PRESSED		70
 #define SONYPI_EVENT_BRIGHTNESS_PRESSED		71
+#define SONYPI_EVENT_MEDIA_PRESSED		72
 
 /* get/set brightness */
 #define SONYPI_IOCGBRT		_IOR('v', 0, __u8)