platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being freed.
Fix this by reordering the kfree() post the dereference.

Fixes: 9d1d3626

 ("platform/x86: ISST: Support partitioned systems")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/r/20240517144946.289615-1-harshit.m.mogalapalli@oracle.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>