[coreboot] [PATCH] BUILD: add -MMD to iasl cpp call

[Peter Stuge]

Sven Schnelle wrote:
> Right now there are no dependency rules for compiling dsdt.asl.
> If ACPI code includes asl files, the dsdt isn't recompiled if any
> of those file is changed. Add the flags to the preprocessor call
> to have it generate the neccessary dependency rule.
> 
> Signed-off-by: Sven Schnelle <svens at stackframe.org>

Acked-by: Peter Stuge <peter at stuge.se>