ath10k: wmi-alloc-chunk should use DMA_BIDIRECTIONAL

These memory chunks are often used as 'swap' by the NIC,
so it will be both reading and writing to these areas.

This seems to fix errors like this on my x86-64 machine:

kernel: DMAR: DMAR:[DMA Write] Request device [05:00.0] fault addr ff5de000
        DMAR:[fault reason 05] PTE Write access is not set

Tested-by: Marek Behun <kabel@blackhole.sk>
Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>