iwlwifi: runtime: add send host command op to firmware runtime op struct

Add send host command op to firmware runtime op struct to allow sending
host commands to the op mode from the fw runtime context.

Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>