Changes to STM32F1 HAL (#8833)

Some to correct missing files from previous PR to completely avoid
HardwareTimer Class (reduce overhead). Some changes to formatting.
Changes to DMA ADC to work correctly.
Change to F1 sanity check.

Marlin/src/HAL/HAL_STM32F1/watchdog_Stm32f1.h

@@ -30,6 +30,12 @@
 #include <libmaple/iwdg.h>
 
 #include "../../../src/inc/MarlinConfig.h"
+
+/**
+ *  The watchdog clock is 40Khz. We need a 4 seconds interval, so use a /256 preescaler and
+ *  625 reload value (counts down to 0)
+ *  use 1250 for 8 seconds
+ */
 #define STM32F1_WD_RELOAD 625
 
 // Arduino STM32F1 core now has watchdog support
@@ -39,6 +45,11 @@ void watchdog_init();
 
 // Reset watchdog. MUST be called at least every 4 seconds after the
 // first watchdog_init or STM32F1 will reset.
-inline void watchdog_reset() { iwdg_feed(); }
+inline void watchdog_reset() {
+  #if PIN_EXISTS(LED)
+    TOGGLE(LED_PIN);  // heart beat indicator
+  #endif
+  iwdg_feed();
+}
 
 #endif // WATCHDOG_STM32F1_H