update_engine: separate update_engine.conf into its own for Chrome OS

Let's have separate files that indicates the minor and major versions
for Chrome OS and Android. This way each system can individually move
the major and minor versions up and down without interfering with each
other.

BUG=b:163153182
TEST=None

Change-Id: Idd3b0f692e88d8592aa8b13c2be65b21ac8efe8e
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2392896
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Tianjie Xu <xunchang@google.com>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Andrew Lassalle <andrewlassalle@chromium.org>
diff --git a/update_engine.conf.chromeos b/update_engine.conf.chromeos
new file mode 100644
index 0000000..af213ad
--- /dev/null
+++ b/update_engine.conf.chromeos
@@ -0,0 +1,2 @@
+PAYLOAD_MAJOR_VERSION=2
+PAYLOAD_MINOR_VERSION=6