ARM: imx: make all pin lists const and signed, move to .init where possible

Making the lists signed fixes sparse warnings like:

	arch/arm/mach-imx/mach-mx27_3ds.c:94:31: warning: incorrect type in argument 1 (different signedness)
	arch/arm/mach-imx/mach-mx27_3ds.c:94:31:    expected int const *pin_list
	arch/arm/mach-imx/mach-mx27_3ds.c:94:31:    got unsigned int static [toplevel] *<noident>

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>