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 not tested on any hardware but the same change was
tested on an APQ8060 DragonBoard with no issues.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>