STM32F1: Restore M43 build support (#17336)

Marlin/src/gcode/config/M43.cpp

     else {
       watchdog_refresh();
       report_pin_state_extended(pin, ignore_protection, true, PSTR("Pulsing   "));
-      const bool prior_mode = GET_PINMODE(pin);
+      #ifdef __STM32F1__
+        const auto prior_mode = _GET_MODE(i);
+      #else
+        const bool prior_mode = GET_PINMODE(pin);
+      #endif
       #if AVR_AT90USB1286_FAMILY // Teensy IDEs don't know about these pins so must use FASTIO
         if (pin == TEENSY_E2) {
           SET_OUTPUT(TEENSY_E2);
           watchdog_refresh();
         }
       }
-      pinMode(pin, prior_mode);
+      #ifdef __STM32F1__
+        _SET_MODE(i, prior_mode);
+      #else
+        pinMode(pin, prior_mode);
+      #endif
     }
     SERIAL_EOL();
   }