mb/cwwk/adl/devicetree: correct PCIe RP 12 clock configuration

Looking at Intel document 759603 revision 001, Alder Lake N only has 5
PCIe clock outputs and clock request pins. I only have the version 2 of
this board which has a significantly different USB port configuration to
version 1, but there the Ethernet controller on RP 11 and the E key m.2
slot on RP 12 share the last PCIe clock output. The on-board TUBF0304
clock buffer chip takes the clock output form the last PCH PCIe clock
generator output and drives the clock inputs of both the last Ethernet
chip and the E key m.2 slot. Since the last clock output is always
active, since RP 11 has the PCIE_RP_CLK_REQ_UNUSED flag set, using the
non-existent clock output and request for RP 12 didn't break things.
ASPM L0s might still work though, since that one doesn't involve
switching off the PCIe reference clock, but haven't tested that yet.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I103f7c3fe0b806f5c0a5202b8221f522a4b1c378
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83911
Reviewed-by: coreboot org <coreboot.org@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/cwwk/adl/devicetree.cb

@@ -42,9 +42,9 @@ chip soc/intel/alderlake
 	}"
 
 	register "pch_pcie_rp[PCH_RP(12)]" = "{
-		.clk_src = 5,
-		.clk_req = 5,
-		.flags = PCIE_RP_LTR | PCIE_RP_AER,
+		.clk_src = 4,
+		.flags = PCIE_RP_LTR | PCIE_RP_AER | PCIE_RP_CLK_REQ_UNUSED,
+		.pcie_rp_aspm = ASPM_DISABLE,
 	}"
 
 	# Enable EDP in PortA