Hi Charles,
I'm focusing in on this error message first:
ACPI Warning: For _SB_.PCI0.LPCB.EC__.LED_: Excess arguments - needs 1, found 2
Can you take a look at the .asl files in your coreboot build? I believe you will find something like "Method (LED, 2, NotSerialized)" which means the LED method wants 2 arguments. Then look for calls to "LED ()" and if you find one only passing 1 argument, that is the problem.
Looking at the decompiled vendor DSDT did not really reveal much in this area, except that it is likely coreboot already has a "clean room" re-implementation of the vendor DSDT since they both use a method called "LED ()"
David