Add customisable EEPROM driver selection (#7274)

- uprintf -> dprintf
- Fix atsam "vendor" eeprom.
- Bump Kinetis K20x to 64 bytes, too.
- Rollback Kinetis to 32 bytes as partitioning can only be done once. Add warning about changing the value.
- Change RAM-backed "fake" EEPROM implementations to match eeconfig's current usage.
- Add 24LC128 by request.

drivers/eeprom/eeprom_driver.h

@@ -0,0 +1,22 @@
+/* Copyright 2019 Nick Brassel (tzarc)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "eeprom.h"
+
+void eeprom_driver_init(void);
+void eeprom_driver_erase(void);