arm: dts: qcom: msm8660: add interrupt controller properties

Add interrupt controller properties now that ssbi-gpio is a proper
hierarchical IRQ chip. The interrupts property is no longer needed so
remove it.

This change was tested on an APQ8060 DragonBoard.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>