include/acpi/acpi.h: Introduce ACPI_DSDT_REV_2 macro

This to replace DSDT revison number with macro so we can adapt all boards
at once if needed.

Change-Id: I9e92a5f408f69aa1a6801bc2cba8ddfe2180b040
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45751
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/include/acpi/acpi.h b/src/include/acpi/acpi.h
index 53308f3..7b0f339 100644
--- a/src/include/acpi/acpi.h
+++ b/src/include/acpi/acpi.h
@@ -41,6 +41,7 @@
 
 #define ACPI_TABLE_CREATOR	"COREBOOT"  /* Must be exactly 8 bytes long! */
 #define OEM_ID			"COREv4"    /* Must be exactly 6 bytes long! */
+#define ACPI_DSDT_REV_2		0x02        /* DSDT revision: ACPI v2.0 and greater */
 
 #if !defined(__ASSEMBLER__) && !defined(__ACPI__)
 #include <commonlib/helpers.h>