libata-core: make sure that ata_force_tbl is freed in case of an error

Fix a potential memory leak when ata_init() encounters an error.

Signed-off-by: Elias Oltmanns <eo@nebensachen.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>