ipq-wifi: drop custom board-2.bins

ipq-wifi: drop custom board-2.bins

The BDFs for all boards were upstreamed to the ath10k-firmware
repository and linux-firmware.git.

We switched to the upstream board-2.bin, hence the files can be removed
here.

Keep the ipq-wifi package in case new boards are added. It might take
some time till board-2.bins send upstream are merged.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
(backported from dceee8cc09a54f96dee82a6e95e3e77a6dd7ac13)