icnss: Add support for WLAN firmware service

iCNSS 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.

Change-Id: If992dbae80f12e1a976bc6e612053cacba1bc716
CRs-Fixed: 914429
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>