Upgrade PRODUCT_SHIPPING_API_LEVEL to 31 (Android S)

PRODUCT_SHIPPING_API_LEVEL: 31
Target FCM version: 5
Kernel FCM version: 6

TO-DO: Upgrade "Target FCM version" from 5 to 6
       "Target FCM version" must be 6 if PRODUCT_SHIPPING_API_LEVEL is 31.

Bug: 167997902
Bug: 186723740
Bug: 184801854
Bug: 186500818
Test: The device can boot to home.
      $ adb shell getprop ro.product.first_api_level
        [ro.product.first_api_level]: [31]
      $ adb shell ls /sys/kernel/debug
      $ adb root && adb shell getprop ro.product.debugfs_restrictions.enabled
Change-Id: I79a9d3835b9d3c508e647c1bbf53bd1c1465de05
Signed-off-by: Aaron Ding <aaronding@google.com>
diff --git a/device.mk b/device.mk
index a7cd966..de12d91 100644
--- a/device.mk
+++ b/device.mk
@@ -216,13 +216,8 @@
 
 DEVICE_PACKAGE_OVERLAYS += device/google/gs101/overlay
 
-# This will be updated to 31 (Android S) for shipping
-PRODUCT_SHIPPING_API_LEVEL := 30
-
-# Enable the debugfs restriction before upgrading shipping abi level to 31 (Android S)
-ifneq (,$(filter userdebug eng, $(TARGET_BUILD_VARIANT)))
-PRODUCT_SET_DEBUGFS_RESTRICTIONS := true
-endif
+# This device is shipped with 31 (Android S)
+PRODUCT_SHIPPING_API_LEVEL := 31
 
 # Enforce the Product interface
 PRODUCT_PRODUCT_VNDK_VERSION := current