ARM: mxs: icoll: Fix sparse warning

Fix the following sparse warning:

arch/arm/mach-mxs/icoll.c:103:13: warning: symbol 'icoll_of_init' was not declared. Should it be static?

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