wr1043nd-v2: Change .code of the wi-fi button to KEY_RFKILL

wr1043nd-v2: Change .code of the wi-fi button to KEY_RFKILL

This patch changes the code of the Wi-Fi On/Off button on the TP-Link WR1043ND v2
from KEY_WLAN to KEY_RFKILL (and renames a few constants to match). The reason
for this change is, that the KEY_WIFI button code is not recognized by the
hotplug subsystem. This means that the userspace is not notified about the
button being pressed which effectively renders it useless.

Signed-off-by: Josef Gajdusek <atx@atx.name>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42922 3c298f89-4303-0410-b956-a3cf2f4a3e73