ath10k: Add support for WCN3990 QMI service

The ath10k snoc driver is a client to WLAN firmware service
started at Q6. Initial control messages to WLAN firmware is
exchanged through QMI interface. This change also adds
the APIs required for WLAN driver to enable and disable
WLAN at firmware.

CRs-Fixed: 2016532
Change-Id: I0572c70db4c693e0d03ed1ad930841a92e60c340
Signed-off-by: Sarada Prasanna Garnayak <sgarna@codeaurora.org>