It has become obvious that switching a number of irqchip drivers
to being platform drivers without considering the platform was a
mistake. We have multiple reports of end-point drivers not
probing because the irqchip driver isn't there yet, breaking
the expectations of the users.

This patch reverts:

920ecb8c ("irqchip/mtk-cirq: Convert to a platform driver")
f97dbf48 ("irqchip/mtk-sysirq: Convert to a platform driver")
5be57099 ("irqchip/qcom-pdc: Switch to using IRQCHIP_PLATFORM_DRIVER helper macros")
95bf9305 ("irqchip/qcom-pdc: Allow QCOM_PDC to be loadable as a permanent module")

and leave QCOM PDC, MTK sysrq and cirq drivers as built-in, special purpose
drivers for the time being until we have worked out a better solution.
Reported-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reported-by: Frank Wunderlich <linux@fw-web.de>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/93debe6a0308b66d3f307af67ba7ec2c@kernel.org