soc/amd/stoneyridge: Add IGFX device ACPI ASL entry

Add internal graphics device 00.01.00 to the ACPI tables so that the
ACPI PCI option ROM save functions have a proper scope to save the
ROM to.

BUG=b:111697181
TEST=Check coreboot log doesn't have "PCI: 00:01.0: Missing ACPI scope"
and check _ROM method is added in the SSDT1.

Change-Id: I2c9ef8d9dff76805b1fcde2ccceef958a5b53b4f
Signed-off-by: Marc Jones <marcj303@gmail.com>
Reviewed-on: https://review.coreboot.org/27653
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/soc/amd/stoneyridge/acpi/northbridge.asl

@@ -46,6 +46,11 @@ Device(AMRT) {
 	Name(_ADR, 0x00000000)
 } /* end AMRT */
 
+/* Internal Graphics */
+Device(IGFX) {
+	Name(_ADR, 0x00010000)
+}
+
 /* Gpp 0 */
 Device(PBR4) {
 	Name(_ADR, 0x00020001)

src/soc/amd/stoneyridge/chip.c

@@ -82,6 +82,8 @@ const char *soc_acpi_name(const struct device *dev)
 		return NULL;
 
 	switch (dev->path.pci.devfn) {
+	case GFX_DEVFN:
+		return "IGFX";
 	case PCIE0_DEVFN:
 		return "PBR4";
 	case PCIE1_DEVFN: