scripts/dts: extract_dts_includes: remove unused 'names' argument

Parameter 'names' is provided as argument of several property
extract functions. Thought it is actually used only once.
Remove when not needed.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>