ARM: OMAP: board-4430sdp: MUX configuration for sys_nirq2

The sys_nirq2 is used for twl6040, make sure the pin is configured
correctly.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>