dlx: Move build.prop entries into the system.prop

Change-Id: Iddd098e06f7c6787d79b058c7f46224e2e47c1f1

Conflicts:

	full_dlx.mk
	system.prop
dlx: system.prop: Remove duplicated entries

These properties are defined elsewhere in the build tree and
we don't need to define them ourselves.

Change-Id: I77f217d40aa4398ba5c7229c3724548e73c5e136