ARM: dts: dra7: Add dt node for the syscon control module wkup

Create a system control module node for the control module portion that
resides under l4_wkup.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>