acpi: Add support for DMAR

The DMA Remapping Reporting (DMAR) table contains information about DMA
remapping.

Add a version simple version of this table with only the minimum fields
filled out. i.e. no entries.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>