ath79: remove kmod-ath9k and wpad from Mikrotik RB750r2

ath79: remove kmod-ath9k and wpad from Mikrotik RB750r2

The RB750r2 (HEXLite) does not have wifi and those packages bloat the image
by a significant amount. When building a custom image with WireGuard and
booting that from initramfs, there wasn't enough space left in tmpfs to
upload and flash the squashfs image. Investigating what packages I could
remove, I discovered these unneeded ones.

Signed-off-by: Eicke Herbertz <wolletd@posteo.de>
Link: https://github.com/openwrt/openwrt/pull/22134
Signed-off-by: Robert Marko <robimarko@gmail.com>
(cherry picked from commit 42cd48678745d5a99720e03595c53230a3c078f9)
Link: https://github.com/openwrt/openwrt/pull/22475
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>