wifi: cfg80211: export DFS CAC time and usable state helper functions

cfg80211 has cfg80211_chandef_dfs_usable() function to know whether
at least one channel in the chandef is in usable state or not. Also,
cfg80211_chandef_dfs_cac_time() function is there which tells the CAC
time required for the given chandef.

Make these two functions visible to drivers by exporting their symbol
to global list of kernel symbols.

Lower level drivers can make use of these two functions to be aware
if CAC is required on the given chandef and for how long. For example
drivers which maintains the CAC state internally can make use of these.

Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>
Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20230912051857.2284-2-quic_adisi@quicinc.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>