ARM: iomux-imx31: allow pin_list to be const

This fixes the following warning in a mx3_defconfig build:

	arch/arm/mach-mx3/mach-bug.c: In function 'bug_board_init':
	arch/arm/mach-mx3/mach-bug.c:47: warning: passing argument 1 of 'mxc_iomux_setup_multiple_pins' discards qualifiers from pointer target type

While at it remove some useless consts from unsigned int arguments.

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