The following build warning is seen with W=1:

warning: no previous prototype for ‘mxc_expio_init’
[-Wmissing-prototypes] int __init mxc_expio_init(u32 base, u32 intr_gpio)

Fix this warning by including "3ds_debugboard.h".
Signed-off-by: Marco Franchi <marco.franchi@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>