dt: bindings: ath10k: add missing dt properties for WCN3990 wifi node

Add missing optional properties in WCN3990 wifi node.

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>