mb/google/brya: Add `ext_pm_support` for taniks eMMC SKU

This patch ensures google/taniks eMMC SKU has advanced PM support
enabled.

BUG=b:235915257
TEST=Able to boot to eMMC SKU to ChromeOS.

Change-Id: I20c98006b6a45e2c8286480c560c8dbc0752327c
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65213
Reviewed-by: Joey Peng <joey.peng@lcfc.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/google/brya/variants/taniks/overridetree.cb b/src/mainboard/google/brya/variants/taniks/overridetree.cb
index 9ce7abb..9a52753 100644
--- a/src/mainboard/google/brya/variants/taniks/overridetree.cb
+++ b/src/mainboard/google/brya/variants/taniks/overridetree.cb
@@ -368,6 +368,7 @@
 				register "enable_gpio" = "ACPI_GPIO_OUTPUT_ACTIVE_HIGH(GPP_D11)"
 				register "reset_gpio" = "ACPI_GPIO_OUTPUT_ACTIVE_LOW(GPP_B4)"
 				register "srcclk_pin" = "0"
+				register "ext_pm_support" = "ACPI_PCIE_RP_EMIT_ALL"
 				device generic 0 on
 					probe BOOT_EMMC_MASK BOOT_EMMC_ENABLED
 				end