BACKPORT: ath10k: enable bus layer suspend/resume for WCN3990

Register snoc bus layer suspend/resume PM ops and configure
the wakeup source(CE2) for the device.

Testing:
    Tested on WCN3990 HW.
    Tested FW: WLAN.HL.2.0-01192-QCAHLSWMTPLZ-1.

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
[govinds@codeaurora.org: fix trivial merge conflicts]
Change-Id: I1116b98f82197a1ee28e094e3b1804aa50227e23
Git-commit: 185be1c66469b2c31bd3a0502b3cdf0e654f95eb
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/ath.git


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