mt76: mt76x0e: don't use hw encryption for MT7630E

Since 41634aa8 ("mt76: only schedule txqs from the tx tasklet")
I can observe firmware hangs on MT7630E on station mode: tx stop
functioning after minor activity (rx keep working) and on module
unload device fail to stop with messages:

[ 5446.141413] mt76x0e 0000:06:00.0: TX DMA did not stop
[ 5449.176764] mt76x0e 0000:06:00.0: TX DMA did not stop

Loading module again results in failure to associate with AP.
Only machine power off / power on cycle can make device work again.

It's unclear why commit 41634aa8 causes the problem, but it is
related to HW encryption. Since issue is a firmware hang, that is super
hard to debug, just disable HW encryption as fix for the issue.

Fixes: 41634aa8

 ("mt76: only schedule txqs from the tx tasklet")
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>