wifi: iwlwifi: change link id in time event to s8

Link ID in time event data is -1 when the time event is cleared.
Change the type of the link ID in the time event data structure
and in the affected function from unsigned to signed.

Fixes: 13506583

 ("wifi: iwlwifi: support link_id in SESSION_PROTECTION cmd")
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Reviewed-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://msgid.link/20240123200528.50d4941f946c.Iea990b118c69bc3e1eb61c1d134c9d470b3a17ac@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>