platform/x86: ISST: unlock on error path in tpmi_sst_init()

Call mutex_unlock(&isst_tpmi_dev_lock) before returning on this
error path.

Fixes: d805456c712f ("platform/x86: ISST: Enumerate TPMI SST and create framework")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/r/dcdebbb7-7de6-4d04-8e7a-43d5ca043484@kili.mountain
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>