ath11k: pci: fix hot reset stability issues

For QCA6390, host needs to reset some registers before MHI power up to fix PCI
link unstable issue if hot reset happened. Also clear all pending interrupts
during power up.

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/1607609124-17250-4-git-send-email-kvalo@codeaurora.org