acpi unit-test: resolved iasl crash

It seems that iasl has an issue when disassembles
some ACPI tables using the command line:
iasl -e DSDT -e SSDT -d HPET

Modified the iasl command line to "iasl -d HPET"
until the problem is solved. The command line
remained the same for DSDT and SSDT tables.

Reported-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
