f2fs: free meta pages if sanity check for ckpt is failed

commit a2125ff7dd1ed3a2a53cdc1f8f9c9cec9cfaa7ab upstream.

This fixes missing freeing meta pages in the error case.

Tested-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>