Fixed reset problem.

To repro the problem:
$Homing/enable=on
<reboot>
$X
<hit a limit switch to cause an ALARM>
^x
<now the command interpreter will not accept characters>

Grbl_Esp32/motion_control.cpp

@@ -435,8 +435,8 @@ void mc_reset() {
         // Kill spindle and coolant.
         spindle->stop();
         coolant_stop();
-        // turn off all digital I/O
-        sys_io_control(0xFF, false);
+        // turn off all digital I/O immediately
+        fast_sys_io_control(0xFF, false);
 #ifdef ENABLE_SD_CARD
         // do we need to stop a running SD job?
         if (get_sd_state(false) == SDCARD_BUSY_PRINTING) {

Grbl_Esp32/system.cpp

@@ -339,8 +339,15 @@ int32_t system_convert_corexy_to_y_axis_steps(int32_t* steps) {
 
 // io_num is the virtual pin# and has nothing to do with the actual esp32 GPIO_NUM_xx
 // It uses a mask so all can be turned of in ms_reset
+// This version waits until realtime commands have been executed
 void sys_io_control(uint8_t io_num_mask, bool turnOn) {
     protocol_buffer_synchronize();
+    fast_sys_io_control(io_num_mask, turnOn);
+}
+
+// This version works immediately, without waiting, to prevent deadlocks.
+// It is used when resetting via mc_reset()
+void fast_sys_io_control(uint8_t io_num_mask, bool turnOn) {
 #ifdef USER_DIGITAL_PIN_1
     if (io_num_mask & bit(1)) {
         digitalWrite(USER_DIGITAL_PIN_1, turnOn);

Grbl_Esp32/system.h

@@ -226,6 +226,7 @@ void controlCheckTask(void* pvParameters);
 void system_exec_control_pin(uint8_t pin);
 
 void sys_io_control(uint8_t io_num_mask, bool turnOn);
+void fast_sys_io_control(uint8_t io_num_mask, bool turnOn);
 
 //
 int8_t sys_get_next_RMT_chan_num();