sm8450-common: Fix user builds
device/qcom/sepolicy_vndr only includes the files that define
vendor_sensors_debug_prop on eng and userdebug builds, so we have to
wrap access to it in a call to userdebug_or_eng.
Change-Id: I4e2662ec29e7ebb4ea1b8616d360307f92e89834
Signed-off-by: Jens Reidel <[email protected]>