clk: mvebu: add missing CESA gate clk

Even if not documented in the datasheet, the Armada 370 SoC can actually
gate the CESA (crypto engine) clock.
Add an entry in the gating_desc table to be able to reference the CESA
gateclk in the crypto node.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>