mtd: harmonize mtd_writev usage

This patch makes the 'mtd_writev()' function more usable and logical. We first
teach it to fall-back to the 'default_mtd_writev()' function if the MTD driver
does not define its own '->writev()' method. Then we make block2mtd and JFFS2
just 'mtd_writev()' instead of 'default_mtd_writev()' function. This means we
can now stop exporting 'default_mtd_writev()' and instead, export
'mtd_writev()'. This is much cleaner and more logical, as well as allows us to
get read of another direct 'mtd->writev' access in JFFS2.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

fs/jffs2/writev.c

@@ -26,11 +26,7 @@ int jffs2_flash_direct_writev(struct jffs2_sb_info *c, const struct kvec *vecs,
 		}
 	}
 
-	if (c->mtd->writev)
-		return mtd_writev(c->mtd, vecs, count, to, retlen);
-	else {
-		return default_mtd_writev(c->mtd, vecs, count, to, retlen);
-	}
+	return mtd_writev(c->mtd, vecs, count, to, retlen);
 }
 
 int jffs2_flash_direct_write(struct jffs2_sb_info *c, loff_t ofs, size_t len,