Import foster init scripts

From NVidia's stock 8.2.0 release for mdarcy.

Also introduce a custom init extension to set relevant
properties.

Lastly, assert on a known supported bootloader.

Change-Id: I9f68361ac7127d8724d29053feb6109547a7deea

BoardConfig.mk

@@ -27,6 +27,12 @@ BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE := ext4
 TARGET_COPY_OUT_VENDOR             := vendor
 BOARD_BUILD_SYSTEM_ROOT_IMAGE      := true
 
+# Assert
+TARGET_OTA_ASSERT_DEVICE := foster
+
+# Bootloader versions
+TARGET_BOARD_INFO_FILE := device/nvidia/foster/board-info.txt
+
 # Kernel
 ifneq ($(TARGET_PREBUILT_KERNEL),)
 BOARD_VENDOR_KERNEL_MODULES += $(wildcard $(dir $(TARGET_PREBUILT_KERNEL))/*.ko)