wifi: mac80211: Allow scan on a radio while operating on DFS on another radio

wifi: mac80211: Allow scan on a radio while operating on DFS on another radio

Currently, in multi-radio wiphy cases, if one radio is operating on a DFS
channel, -EBUSY is returned even when a scan is requested on a different
radio. Because of this, an MLD AP with one radio (link) on a DFS channel
and Automatic Channel Selection (ACS) on another radio (link) cannot be
brought up.

In multi-radio wiphy cases, multiple radios are grouped under a single
wiphy. Hence, if a radio is operating on a DFS channel and a scan is
requested on a different radio of the same wiphy, the scan can be allowed
simultaneously without impacting the DFS operations.

Add logic to check the underlying radio used for the requested scan. If the
radio on which DFS is already running is not being used, allow the scan
operation; otherwise, return -EBUSY.

Signed-off-by: Raj Kumar Bhagat <quic_rajkbhag@quicinc.com>
Link: https://patch.msgid.link/20250527-mlo-dfs-acs-v2-3-92c2f37c81d9@quicinc.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>