ARM: dts: Fix igepv5 audiopwon-gpio

Playing audio works on omap5-uevm, but produces an "Unhandled fault:
imprecise external abort (0x1406) at 0x00000000" error on igepv5.

Looks like the twl6040 audpwron GPIO pin is different for these
boards. Let's fix the issue by configuring the audpwron in the
board specific dts file.

Cc: Agustí Fontquerni <af@iseebcn.com>
Cc: Eduard Gavin <egavin@iseebcn.com>
Cc: Enric Balletbo i Serra <eballetbo@gmail.com>
Acked-by: Peter Ujfalusi <peter.ujflausi@ti com>
Signed-off-by: Tony Lindgren <tony@atomide.com>