ath11k: refactor multiple MSI vector implementation

This is to prepare for one MSI vector support. IRQ enable and disable
of CE and DP are done only in case of multiple MSI vectors.

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>
Signed-off-by: Baochen Qiang <bqiang@codeaurora.org>
Link: https://lore.kernel.org/r/20211026041705.5167-1-bqiang@codeaurora.org