irqchip/qcom-pdc: Reset PDC interrupts during init

Kexec can directly boot into a new kernel without going to complete
reboot. This can leave the previous kernel's configuration for PDC
interrupts as is.

Clear previous kernel's configuration during init by setting interrupts
in enable bank to zero. The IRQs specified in qcom,pdc-ranges property
are the only ones that can be used by the new kernel so clear only those
IRQs. The remaining ones may be in use by a different kernel and should
not be set by new kernel.

Suggested-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Tested-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/1601267524-20199-7-git-send-email-mkshah@codeaurora.org