Reland "Add microdroid_vendor"

This reverts commit c79d1dc7ebd40d182816ecb4baaa1c0b6afa8b2a.

Reason for revert: relanding

Change-Id: I38b51ef26e62900f5f14230b1c08681ea7871d13
diff --git a/microdroid/plat_sepolicy_vers.txt b/microdroid/plat_sepolicy_vers.txt
new file mode 100644
index 0000000..36c9030
--- /dev/null
+++ b/microdroid/plat_sepolicy_vers.txt
@@ -0,0 +1 @@
+10000.0