acpi: Move the xsdt pointer to acpi_ctx

Put this in the context along with the other important pointers.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
diff --git a/include/dm/acpi.h b/include/dm/acpi.h
index c6c63b8..7563a4c 100644
--- a/include/dm/acpi.h
+++ b/include/dm/acpi.h
@@ -33,11 +33,13 @@
  * @rsdp: Pointer to the Root System Description Pointer, typically used when
  *	adding a new table. The RSDP holds pointers to the RSDT and XSDT.
  * @rsdt: Pointer to the Root System Description Table
+ * @xsdt: Pointer to the Extended System Description Table
  */
 struct acpi_ctx {
 	void *current;
 	struct acpi_rsdp *rsdp;
 	struct acpi_rsdt *rsdt;
+	struct acpi_xsdt *xsdt;
 };
 
 /**