Exposes PcieRpL1Substates to devicetree to allow boards to override this configuration. Tested on an Acer Aspire VN7-572G (Skylake-U). Change-Id: I36150858485715016158595c832c142b0582ddb8 Signed-off-by: Benjamin Doron <benjamin.doron00@gmail.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/39538 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Nico Huber <nico.h@gmx.de>