ath11k: peer delete synchronization with firmware

Peer creation in firmware fails, if last peer deletion
is still in progress.
Hence, add wait for the event after deleting every peer
from host driver to synchronize with firmware.

Signed-off-by: Ritesh Singh <ritesi@codeaurora.org>
Signed-off-by: Maharaja Kennadyrajan <mkenna@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1605514143-17652-3-git-send-email-mkenna@codeaurora.org

(imported from commit 690ace20)