wifi: cfg80211: make cluster id an array

wifi: cfg80211: make cluster id an array

cfg80211_nan_conf::cluster_id is currently a pointer, but there is no real
reason to not have it an array. It makes things easier as there is no
need to check the pointer validity each time.
If a cluster ID wasn't provided by user space it will be randomized.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260302091108.2b12e4ccf5bb.Ib16bf5cca55463d4c89e18099cf1dfe4de95d405@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>