irqchip/qcom-pdc: Switch to IRQCHIP_PLATFORM_DRIVER and allow as a module

This patch revives changes from Saravana Kannan to switch the
qcom-pdc driver to use IRQCHIP_PLATFORM_DRIVER helper macros,
and allows qcom-pdc driver to be loaded as a permanent module.

Earlier attempts at this ran into trouble with loading
dependencies, but with Saravana's fw_devlink=on set by default
now we should avoid those.

[jstultz: Folded in with my changes to allow the driver to be
 loadable as a permenent module]

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Maulik Shah <mkshah@codeaurora.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org
Signed-off-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210518211922.3474368-1-john.stultz@linaro.org