mb/google/brox/var/brox: Enable ASPM for PCIe4 SSD of CPU

Check that lnkCap supports ASPM L1, so set it to ASPM_L1
to avoid excessive power consumption.

BUG=b:363854853
TEST=emerge-brox sys-boot/coreboot sys-boot/chromeos-bootimage

Change-Id: I386f8e88a5af661b1f4c04d2e2a34cd181608bd8
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84278
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: <srinivas.kulkarni@intel.com>

src/mainboard/google/brox/variants/brox/overridetree.cb

@@ -273,6 +273,7 @@ chip soc/intel/alderlake
 				.clk_req = 3,
 				.clk_src = 3,
 				.flags = PCIE_RP_LTR | PCIE_RP_AER,
+				.pcie_rp_aspm = ASPM_L1
 			}"
 			probe STORAGE STORAGE_NVME
 			probe unprovisioned