ARM: mxs: ocotp: Fix sparse warning

Include <mach/common.h> header to fix the following sparse warning:

arch/arm/mach-mxs/ocotp.c:33:11: warning: symbol 'mxs_get_ocotp' 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>