hw/arm/virt-acpi-build: _CCA attribute is compulsory

According to ACPI specification 6.2.17 _CCA (Cache Coherency Attribute)
this attribute is compulsory on ARM systems. Add this attribute to
the PCI host bridges as required.

Without this the kernel will produce the error
[Firmware Bug]: PCI device 0000:00:00.0 fail to setup DMA.

Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org>
Message-id: 1446460786-13663-1-git-send-email-graeme.gregory@linaro.org
Reviewed-by: Shannon Zhao <shannon.zhao@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/virt-acpi-build.c

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 1aaff1f..1430125 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -180,6 +180,7 @@
     aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
     aml_append(dev, aml_name_decl("_UID", aml_string("PCI0")));
     aml_append(dev, aml_name_decl("_STR", aml_unicode("PCIe 0 Device")));
+    aml_append(dev, aml_name_decl("_CCA", aml_int(1)));
 
     /* Declare the PCI Routing Table. */
     Aml *rt_pkg = aml_package(nr_pcie_buses * PCI_NUM_PINS);