Hide freeMemory et.al. warnings

Marlin/src/HAL/HAL_STM32F1/HAL.h

@@ -180,11 +180,17 @@ static int freeMemory() {
   return top;
 }
 */
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
+
 static int freeMemory() {
   volatile char top;
   return &top - reinterpret_cast<char*>(_sbrk(0));
 }
 
+#pragma GCC diagnostic pop
+
 //
 // SPI: Extended functions which take a channel number (hardware SPI only)
 //

Marlin/src/HAL/HAL_STM32F1/persistent_store_sdcard.cpp

@@ -62,7 +62,7 @@ bool PersistentStore::access_finish() {
 }
 
 bool PersistentStore::write_data(int &pos, const uint8_t *value, const size_t size, uint16_t *crc) {
-  for (int i = 0; i < size; i++)
+  for (size_t i = 0; i < size; i++)
     HAL_STM32F1_eeprom_content[pos + i] = value[i];
   crc16(crc, value, size);
   pos += size;
@@ -70,7 +70,7 @@ bool PersistentStore::write_data(int &pos, const uint8_t *value, const size_t si
 }
 
 bool PersistentStore::read_data(int &pos, uint8_t* value, const size_t size, uint16_t *crc, const bool writing/*=true*/) {
-  for (int i = 0; i < size; i++) {
+  for (size_t i = 0; i < size; i++) {
     uint8_t c = HAL_STM32F1_eeprom_content[pos + i];
     if (writing) value[i] = c;
     crc16(crc, &c, 1);