Use MAX_BED_POWER instead of BANG_MAX to heat outside PID_FUNCTIONAL_RANGE (#15431)

Marlin/src/module/temperature.cpp

         pid_reset = true;
       }
       else if (pid_error > PID_FUNCTIONAL_RANGE) {
-        pid_output = BANG_MAX;
+        pid_output = MAX_BED_POWER;
         pid_reset = true;
       }
       else {