mtd: nand: Fix memory leak on txx9ndfmc probe failure.

mtd: nand: Fix memory leak on txx9ndfmc probe failure.

Commit 81933046ef2a615031c46171013bde2c5225ee69 ('mtd: Fix handling of
mtdname in txx9ndfmc.c') introduced a potential memory leak. The
'mtdname' member of the private data structure is now allocated
separately, but was not freed on certain error paths.

Fix that, and make things simpler by _always_ allocating it separately
so that we don't need 'if (mtdname != dev_name()) kfree(mtdname);'...
which gets ugly now that we're doing it more than once, and more likely
that we'll get it wrong some time.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>