ath11k: put target to wow state when suspend happens

This change is to put QCA6390 to wow state instead of suspend state
when system suspend happens. It also disables CE irq and DP irq, and
then put MHI to suspend state.

When system resumes, driver resumes MHI firstly, then enables CE irq
and dp IRQ, and sends wow wakeup command to firmware.

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>