wifi: mac80211: tests: add utility to create sdata skeleton

Some functions that should be tested may expect an sdata object that is
configured to a basic degree. Add setup code to create such an object
for use by tests.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250101070249.12eeefd3c98b.I6e8c2b8374d4305f16675524ca30621e089b6fb0@changeid


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