acpi/gpex: Fix cca attribute check for pxb device

acpi/gpex: Fix cca attribute check for pxb device

When check DMA support for device attached to pxb,
the cache coherency attribute need to be set.
This add _CCA attribute for pxb DSDT.

Fixes: 6f9765fbad ("acpi/gpex: Build tables for pxb")

Signed-off-by: Jiahui Cen <cenjiahui@huawei.com>
Signed-off-by: Xingang Wang <wangxingang5@huawei.com>
Message-Id: <1612490205-48788-3-git-send-email-wangxingang5@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>