mb/google/sarien: Turn on ASPM L1.2 for Card Reader

Enable ASPM L1.2 support for embedded realtek card reader, after change
the power consumption for SD controller from 5mW to less than 2mW.

BUG=N/A
TEST=Build and boot up on Arcada platform, check the PCI configuration
on pcie root port offset 0x208 is 0x0f, and offset 0x168 on card reader
is also 0x0f.

Signed-off-by: Lijian Zhao <lijian.zhao@intel.com>
Change-Id: I08d85ee332ceee8ed85cd816bc3e6c895528fdb0
Reviewed-on: https://review.coreboot.org/c/31145
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Roy Mingi Park <roy.mingi.park@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/sarien/variants/arcada/devicetree.cb

@@ -100,6 +100,7 @@ chip soc/intel/cannonlake
 
 	# PCIe port 11 for card reader
 	register "PcieRpEnable[10]" = "1"
+	register "PcieRpLtrEnable[10]" = "1"
 	register "PcieClkSrcUsage[1]" = "10"
 	register "PcieClkSrcClkReq[1]" = "1"
 

src/mainboard/google/sarien/variants/sarien/devicetree.cb

@@ -99,6 +99,7 @@ chip soc/intel/cannonlake
 
 	# PCIe port 8 for Card Reader
 	register "PcieRpEnable[7]" = "1"
+	register "PcieRpLtrEnable[7]" = "1"
 	register "PcieClkSrcUsage[4]" = "7"
 	register "PcieClkSrcClkReq[4]" = "4"