mtd: memory corruption in block2mtd.c

The block2mtd driver (drivers/mtd/devices/block2mtd.c) will kfree an on-stack
pointer when handling an invalid argument line (e.g.
block2mtd=/dev/loop0,xxx).

The kfree was added some time ago when "name" was dynamically allocated.

Signed-off-by: Ingo van Lil <inguin@gmx.de>
Acked-by: Joern Engel <joern@lazybastard.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: <stable@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>