[MTD] Initialize 'writesize'

Signed-off-by: Artem B. Bityutskiy <dedekind@infradead.org>
diff --git a/drivers/mtd/chips/map_ram.c b/drivers/mtd/chips/map_ram.c
index 7639257..3a66680 100644
--- a/drivers/mtd/chips/map_ram.c
+++ b/drivers/mtd/chips/map_ram.c
@@ -71,6 +71,7 @@
 	mtd->write = mapram_write;
 	mtd->sync = mapram_nop;
 	mtd->flags = MTD_CAP_RAM;
+	mtd->writesize = 1;
 
 	mtd->erasesize = PAGE_SIZE;
  	while(mtd->size & (mtd->erasesize - 1))