mmc_block: fix probe error cleanup bug

If mmc_blk_set_blksize() fails mmc_blk_probe() the request queue and its
thread have been set up and they need to be shut down properly before
putting the disk.

Signed-off-by: Jarkko Lavinen <jarkko.lavinen@nokia.com>
Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Cc: <linux-mmc@vger.kernel.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>