ARM: mach-imx: src: Include "common.h

Fix the following sparse warnings:

arch/arm/mach-imx/src.c:28:6: warning: symbol 'imx_enable_cpu' was not declared. Should it be static?
arch/arm/mach-imx/src.c:39:6: warning: symbol 'imx_set_cpu_jump' was not declared. Should it be static?
arch/arm/mach-imx/src.c:46:6: warning: symbol 'imx_src_prepare_restart' was not declared. Should it be static?
arch/arm/mach-imx/src.c:59:13: warning: symbol 'imx_src_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>