Fix the following sparse warnings:

drivers/clk/mxs/clk-imx28.c:72:5: warning: symbol 'mxs_saif_clkmux_select' was not declared. Should it be static?
drivers/clk/mxs/clk-imx28.c:156:12: warning: symbol 'mx28_clocks_init' was not declared. Should it be static?
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Acked-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NMike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: fixed $SUBJECT line]