ath11k: hif: implement suspend and resume functions

For suspend support add suspend and resume to HIF layer. These ops are optional
and, for example, AHB bus driver does not need to implement these.

Tested-on: QCA6390 hw2.0 PCI WLAN.HST.1.0.1-01740-QCAHSTSWPLZ_V2_TO_X86-1

Signed-off-by: Carl Huang <cjhuang@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1607708150-21066-3-git-send-email-kvalo@codeaurora.org