ath79-generic: remove workaround

Now that OpenWrt implements a proper fix for the stalled boots on 74kc
boards, the previous workaround can be removed.

Signed-off-by: David Bauer <mail@david-bauer.net>

targets/ath79-generic

--- modify kernel builds slightly to work around a boot hang on various device
--- based on the QCA9563 SoC - especially the Unifi AC-* devices
-config('KERNEL_AIO', true)
-
 -- enforce mainline ath10k kmod/firmware over openwrt default ath10k-ct usage
 -- ath10k-ct is unstable/broken with 11s meshing, works only wave2 chipsets