Optimize emergency parser check

Marlin/src/gcode/queue.cpp

@@ -538,12 +538,11 @@ void GCodeQueue::get_serial_commands() {
 
         #if DISABLED(EMERGENCY_PARSER)
           // Process critical commands early
-          if (strcmp_P(command, PSTR("M108")) == 0) {
+          if (command[0] == 'M') switch (command[3]) {
-            wait_for_heatup = false;
+            case '8': if (command[2] == '0' && command[1] == '1') { wait_for_heatup = false; TERN_(HAS_LCD_MENU, wait_for_user = false); } break;
-            TERN_(HAS_LCD_MENU, wait_for_user = false);
+            case '2': if (command[2] == '1' && command[1] == '1') kill(M112_KILL_STR, nullptr, true); break;
+            case '0': if (command[1] == '4' && command[2] == '1') quickstop_stepper(); break;
           }
-          if (strcmp_P(command, PSTR("M112")) == 0) kill(M112_KILL_STR, nullptr, true);
-          if (strcmp_P(command, PSTR("M410")) == 0) quickstop_stepper();
         #endif
 
         #if defined(NO_TIMEOUTS) && NO_TIMEOUTS > 0