clk: mxs: clk-imx23: Include <linux/clk/mxs.h>

Fix the following sparse warning:

drivers/clk/mxs/clk-imx23.c:102:12: warning: symbol 'mx23_clocks_init' was not declared. Should it be static?

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>