Use omap specific pinctrl defines (OMAP3_CORE1_IOPAD) to configure
the padconf register offset.

This simplify further support of CompuLab's boards based on omap36xx,
omap34xx and am35x.
Signed-off-by: Dmitry Lifshitz <lifshitz@compulab.co.il>
Signed-off-by: Tony Lindgren <tony@atomide.com>