ACPI: Use common OperationRegion for PCI_MMCONF

Change-Id: Iadb4c3c77ecda4df8e48415d246e769ede2ce86d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50648
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/acpi/dsdt_top.asl

@@ -32,9 +32,14 @@ Method (_PIC, 1)
 }
 
 #if CONFIG(MMCONF_SUPPORT)
-/* Base address of PCIe config space */
-Name(PCBA, CONFIG_MMCONF_BASE_ADDRESS)
+Scope(\_SB) {
+	/* Base address of PCIe config space */
+	Name(PCBA, CONFIG_MMCONF_BASE_ADDRESS)
 
-/* Length of PCIe config space, 1MB each bus */
-Name(PCLN, CONFIG_MMCONF_LENGTH)
+	/* Length of PCIe config space, 1MB each bus */
+	Name(PCLN, CONFIG_MMCONF_LENGTH)
+
+	/* PCIe Configuration Space */
+	OperationRegion(PCFG, SystemMemory, PCBA, PCLN) /* Each bus consumes 1MB */
+}
 #endif