x86: Allow devices to write to DSDT

Call the new core function to inject ASL programmatically into the DSDT.
This is made up of fragments generated by devices that have the
inject_dsdt() method. The normal, compiled ASL file is added after this.

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