clk: imx6q: add DCICx clocks gate

On i.MX6QP/i.MX6Q/i.MX6DL, there are DCIC1/DCIC2 clocks
gate in CCM_CCGR0 register, add them into clock tree for
clock management.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>