prebuilt/wifi: update ath6kl to CMTP v4.5

v4.4.1 disabled "scheduled-scan"
v4.5   reworks how WOW is handled
see https://github.com/TouchpadCM/compat-wireless-3.5-rc3-1-sn

Change-Id: Idfa98cc23cccba31c44d8f8cc3f193d9a58a1bd7
rm outdated README

Change-Id: I57fd4b2d7864530378ba841bc1646023b624aafd