AP_Gripper: add parameter unit and remove print on grab or release

libraries/AP_Gripper/AP_Gripper.cpp

@@ -52,6 +52,7 @@ const AP_Param::GroupInfo AP_Gripper::var_info[] = {
     // @Description: Time in seconds that gripper will regrab the cargo to ensure grip has not weakened; 0 to disable
     // @User: Advanced
     // @Values: 0 255
+    // @Units: seconds
     AP_GROUPINFO("REGRAB",  5, AP_Gripper, config.regrab_interval, GRIPPER_REGRAB_DEFAULT),
 
     // @Param: UAVCAN_ID

libraries/AP_Gripper/AP_Gripper_EPM.cpp

@@ -48,7 +48,6 @@ void AP_Gripper_EPM::grab()
 
 #ifdef UAVCAN_IOCS_HARDPOINT_SET
     if (should_use_uavcan()) {
-        ::printf("EPM: UAVCAN GRAB\n");
         const UAVCANCommand cmd = make_uavcan_command(1);
         (void)ioctl(_uavcan_fd, UAVCAN_IOCS_HARDPOINT_SET, reinterpret_cast<unsigned long>(&cmd));
     }
@@ -71,7 +70,6 @@ void AP_Gripper_EPM::release()
 
 #ifdef UAVCAN_IOCS_HARDPOINT_SET
     if (should_use_uavcan()) {
-        ::printf("EPM: UAVCAN RELEASE\n");
         const UAVCANCommand cmd = make_uavcan_command(0);
         (void)ioctl(_uavcan_fd, UAVCAN_IOCS_HARDPOINT_SET, reinterpret_cast<unsigned long>(&cmd));
     }