modularize dmd

Bug: 190331463
Test: build ROM and make sure dmd is launched
Change-Id: Ie7ee06cbefeced5a69292e22012f533296081319
diff --git a/modem/user.mk b/modem/user.mk
new file mode 100644
index 0000000..81f3773
--- /dev/null
+++ b/modem/user.mk
@@ -0,0 +1,2 @@
+PRODUCT_PACKAGES += dmd
+BOARD_VENDOR_SEPOLICY_DIRS += device/google/gs101-sepolicy/modem/user