mb/intel/adlrvp: Enable RTD3 root port mutex for WWAN

This adds RTD3 RPMX mutex to the root port. It is shared between RTD3
and WWAN. The purpose of using this mutex is to prevent OSPM from
calling _ON and _OFF methods while WWAN kernel driver is calling _RST,
which accesses the GPIO pins.

BUG=NA
BRANCH=firmware-brya-14505.B
TEST=boot to OS and check the generated SSDT table for the root port.
The RPMX mutex should be generated under the root port.

Signed-off-by: Cliff Huang <cliff.huang@intel.com>
Change-Id: I809eb84cb1a09deb168040e83041b65237a1b576
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73383
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Bora Guvendik <bora.guvendik@intel.com>

src/mainboard/intel/adlrvp/variants/adlrvp_p_ext_ec/overridetree.cb

@@ -70,6 +70,7 @@ chip soc/intel/alderlake
 				register "srcclk_pin" = "5"
 				register "ext_pm_support" = "ACPI_PCIE_RP_EMIT_ALL"
 				register "skip_on_off_support" = "true"
+				register "use_rp_mutex" = "true"
 				device generic 0 alias rp6_rtd3 on
 				end
 			end

src/mainboard/intel/adlrvp/variants/adlrvp_rpl_ext_ec/overridetree.cb

@@ -70,6 +70,7 @@ chip soc/intel/alderlake
 				register "srcclk_pin" = "5"
 				register "ext_pm_support" = "ACPI_PCIE_RP_EMIT_ALL"
 				register "skip_on_off_support" = "true"
+				register "use_rp_mutex" = "true"
 				device generic 0 alias rp6_rtd3 on
 				end
 			end