arm: dts: qcom: mdm9615: 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.

Note that the IRQs started at 24 instead of 192 like all of the other
PMICs. This is the same IRQs as the MPP for this board. qcom-pm8xxx.c
doesn't set the shared IRQs so this is highly likely to be a copy and
paste error.

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