wifi: ath12k: fix regulatory init race condition

wmi code uses ATH12K_FLAG_REGISTERED to decide whether regd message
from firmware is the default one sent during firmware registration, or
response to user request.

As soon as mac80211 phy is registered, regulatory notifier is
immediately called to apply currently configured global regdomain, a
wmi message to update regdomain will be sent to firmware.

ATH12K_FLAG_REGISTERED is not set immediately after phy registration,
the wmi message response can arrive before it is set.

In that case wmi code will update default_regd instead new_regd, and
won't queue regd_update_work. The phy regdomain will stay at the
default value, ignoring the mac80211 request to change it.

Fix this by keeping track of pending user request.

Also avoid double update of regdomain at init, if we know a user
request to change it is in flight.

Signed-off-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Suraj P Kizhakkethil <quic_surapk@quicinc.com>
Signed-off-by: Raj Kumar Bhagat <quic_rajkbhag@quicinc.com>
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>