ARM: dts: qcom: pm8941: add interrupt controller properties

Add interrupt controller properties now that spmi-gpio is a proper
hierarchical IRQ chip. The interrupts property is no longer needed so
remove it. Code was tested on the LG Nexus 5 (hammerhead) phone.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>