mtd: block2mtd: fix recursive call of mtd_writev

The 'mtd_writev' interface calls the function assigned
to the '_write' field of a given mtd device if that is
not NULL. The block2mtd driver sets the '_writev' field
to the 'mtd_writev' function itself and thus causes a
endless loop.

This is caused by 1dbebd32562b3c2caeca35960e5cb00bfcc12900
(mtd: harmonize mtd_writev usage).

Remove the assignment from the block2mtd driver to fix the
issue.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: stable@kernel.org [3.3+]
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/devices/block2mtd.c

@@ -265,7 +265,6 @@ static struct block2mtd_dev *add_device(char *devname, int erase_size)
 	dev->mtd.flags = MTD_CAP_RAM;
 	dev->mtd._erase = block2mtd_erase;
 	dev->mtd._write = block2mtd_write;
-	dev->mtd._writev = mtd_writev;
 	dev->mtd._sync = block2mtd_sync;
 	dev->mtd._read = block2mtd_read;
 	dev->mtd.priv = dev;