wifi: cfg80211: wext: convert return value to kernel-doc

Since I'm getting a warning here right now, fix the
kernel-doc to be "Returns:" rather than just writing
that out in the doc paragraph.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230928172905.ab3b9274bf07.If263f9f6726d6ad4661f8603e6a4485e0385d67f@changeid


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