NFC: Add a target lost netlink event

Some chips are capable of detecting when a tag is out of the field, so
they could send a netlink event about it to userspace.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/nfc.h

@@ -70,6 +70,7 @@ enum nfc_commands {
 	NFC_EVENT_TARGETS_FOUND,
 	NFC_EVENT_DEVICE_ADDED,
 	NFC_EVENT_DEVICE_REMOVED,
+	NFC_EVENT_TARGET_LOST,
 /* private: internal use only */
 	__NFC_CMD_AFTER_LAST
 };