ath10k: Add SNOC bus type for WCN3990 target

WCN3990 is integrated chipset which uses system NOC.
Add SNOC bus type and related definitions.

Signed-off-by: Govind Singh <govinds@qti.qualcomm.com>
Signed-off-by: Rakesh Pillai <pillair@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>