mb/google/brya: enable PCIe RP12 for lisbon eMMC support

BUG=b:246657849
TEST=FW_NAME=lisbon emerge-brask coreboot

Signed-off-by: Kevin Chiu <kevin.chiu.17802@gmail.com>
Change-Id: Ief8ca9cf845156ac761556d0eb49edb65894c001
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68167
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ricky Chang <rickytlchang@google.com>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>

src/mainboard/google/brya/variants/lisbon/overridetree.cb

@@ -200,6 +200,14 @@ chip soc/intel/alderlake
 				device generic 0 on end
 			end
 		end	#PCIE8 SD card
+		device ref pcie_rp12 on
+			# Enable PCIE eMMC bridge 12 using clk 4
+			register "pch_pcie_rp[PCH_RP(12)]" = "{
+				.clk_src = 4,
+				.clk_req = 4,
+				.flags = PCIE_RP_HOTPLUG | PCIE_RP_AER,
+			}"
+		end     #PCIE12 EMMC
 		device ref gspi1 off end
 		device ref pch_espi on
 			chip ec/google/chromeec