ARM: dts: DRA7: switch to compatible pinctrl

Now that ti,dra7-padconf is available, switch over to that compatible
property. Retain pinctrl-single for legacy support.

While at it, mark pinctrl as interrupt controller so that it can be used
with interrupts-extended property for wakeup events.

Signed-off-by: Nishanth Menon <nm@ti.com>