ar71xx-generic: prefer kmod-ath10k for 802.11s mesh (#1499)

removes cryptic debug messages from kernel ring buffer and
also reduces memory usage by as much as 20-25 MiB.

targets/ar71xx-generic

 config 'CONFIG_GLUON_SPECIALIZE_KERNEL=y'
 
-ATH10K_PACKAGES='-kmod-ath10k kmod-ath10k-ct'
+ATH10K_PACKAGES=
 ATH10K_PACKAGES_QCA9887=
 if [ "$GLUON_WLAN_MESH" = 'ibss' ]; then
 	ATH10K_PACKAGES='-kmod-ath10k kmod-ath10k-ct -ath10k-firmware-qca988x ath10k-firmware-qca988x-ct'