imx6qdl-wandboard.dtsi: Fix GPIO pins setup for a saner value

The GPIO pins where not behaving as expected. The SION flag were not
set and the MUX value didn't use the usual default. This commit
changes it to use 0x4001b0b0.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: CruX <crux@project-insanity.org>