acpi: Enable pxb unit-test for ARM virt machine

acpi: Enable pxb unit-test for ARM virt machine

No matter whether the pxb is enabled or not, the CONFIG_PXB macro in test
would keep undefined. And since pxb is now enabled for ARM Virt machine
by default, let's enable pxb unit-test by removing the CONFIG_PXB.

Acked-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Jiahui Cen <cenjiahui@huawei.com>
Message-Id: <20210114100643.10617-8-cenjiahui@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>