ath10k: add QMI message handshake for wcn3990 client

Add WCN3990 QMI client handshakes for Q6 integrated WLAN connectivity
subsystem. This layer is responsible for communicating qmi control
messages to wifi fw QMI service using QMI messaging protocol.

Qualcomm MSM Interface(QMI) is a messaging format used to communicate
between components running between remote processors with underlying
transport layer based on integrated chipset(shared memory) or
discrete chipset(PCI/USB/SDIO/UART).

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Niklas Cassel <niklas.cassel@linaro.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>