staging: imx: fix non-static declarations

Add static keywords to fix this kind of sparse warnings:
warning: symbol 'imx_t_vcm_timing' was not declared. Should it be static?

Signed-off-by: JB Van Puyvelde <jbvanpuyvelde@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>