acpi: Add define for GTDT

Add the interrupt flag used in ACPI GTDT table as define.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Moritz Fischer <moritzf@google.com>

include/acpi/acpi_table.h

@@ -707,6 +707,8 @@ struct acpi_gtdt {
 	u32 virt_el2_flags;
 } __packed;
 
+#define GTDT_FLAG_INT_ACTIVE_LOW	BIT(1)
+
 /**
  * struct acpi_bgrt -  Boot Graphics Resource Table (BGRT)
  *