Add missing lock that is protecting relay->incoming_actions.

Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240603081723.18775-1-nirmoy.das@intel.comSigned-off-by: Nirmoy Das <nirmoy.das@intel.com>