clk: imx6sx: disable unnecessary clocks during clock initialization

Disable those unnecessary clocks during kernel boot up to save power,
those modules clock should be managed by modules driver in runtime.

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