boards/native: Configure write_size in MTD device

boards/native/board_init.c

@@ -27,6 +27,7 @@ mtd_native_dev_t mtd0_dev = {
         .sector_count = MTD_SECTOR_NUM,
         .pages_per_sector = MTD_SECTOR_SIZE / MTD_PAGE_SIZE,
         .page_size = MTD_PAGE_SIZE,
+        .write_size = MTD_WRITE_SIZE,
     },
     .fname = MTD_NATIVE_FILENAME,
 };

boards/native/include/board.h

@@ -76,6 +76,11 @@ void _native_LED_RED_TOGGLE(void);
 #ifndef MTD_SECTOR_NUM
 #define MTD_SECTOR_NUM          (2048)
 #endif
+/** Advertised write size. While the file system backend supports single byte
+ * granularity, this can be increased to mimic other media. */
+#ifndef MTD_WRITE_SIZE
+#define MTD_WRITE_SIZE          (1)
+#endif
 #ifndef MTD_NATIVE_FILENAME
 #define MTD_NATIVE_FILENAME     "MEMORY.bin"
 #endif