ath11k: Refactor ath11k_msi_config

Move ath11k_msi_config to array of structures to add multiple
pci devices support. No functional changes.

Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.4.0.1.r2-00012-QCAHKSWPL_SILICONZ-1

Signed-off-by: Anilkumar Kolli <akolli@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1612946530-28504-2-git-send-email-akolli@codeaurora.org