clk: clk-divider: Export clk_register_divider()

clk_register_divider() needs to be exported so that it could be used
in a module driver, otherwise we get the following error:

ERROR: "clk_register_divider" [sound/soc/mxs/snd-soc-mxs.ko] undefined!

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: also export clk_register_divider_table]