clk: clock-local2: Support parsing gate-clocks from dt

Similar to the cbc clock, the gate-clock also allows
enabling/disabling clock signals. However, no hw
feedback signal is available.

Change-Id: Ia2e4484ab817c603a810cf33b6f27ef73cf6b9c6
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>