HID: input: don't register unmapped input devices

There is no need to register an input device containing no events.
This allows drivers using the quirk MULTI_INPUT to register one input
per report effectively used.

For backward compatibility, we need to add a quirk to request
this behavior.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 863744c..fffa06b 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -282,6 +282,7 @@
 #define HID_QUIRK_BADPAD			0x00000020
 #define HID_QUIRK_MULTI_INPUT			0x00000040
 #define HID_QUIRK_HIDINPUT_FORCE		0x00000080
+#define HID_QUIRK_NO_EMPTY_INPUT		0x00000100
 #define HID_QUIRK_SKIP_OUTPUT_REPORTS		0x00010000
 #define HID_QUIRK_FULLSPEED_INTERVAL		0x10000000
 #define HID_QUIRK_NO_INIT_REPORTS		0x20000000