ath10k: platform driver for WCN3990 SNOC WLAN module

WCN3990 is integrated 802.11ac chipset with SNOC
bus interface. Add snoc layer driver registration
and associated ops.

WCN3990 support is not yet complete as cold-boot
handshake is done using qmi(Qualcomm-MSM-Interface)
and qmi client support will be added once qmi framework
is available.

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>