arm/dts: Add pinctrl driver entries for omap2/3/4

Add pinctrl driver entries for omap2+. These all use
the generic pinctrl-single driver for the padconf
registers.

Cc: devicetree-discuss@lists.ozlabs.org
Acked-by: Linus Walleij <linus.walleij@linaro.org>
[tony@atomide.com: updated to drop omap2420.dtsi rename changes]
Signed-off-by: Tony Lindgren <tony@atomide.com>