ARM: EXYNOS: Clear OF_POPULATED flag from PMU node in IRQ init callback

The Exynos PMU node is an interrupt, clock and PMU (Power Management Unit)
controller, and these functionalities are supported by different drivers
that matches the same compatible strings.

Since commit 15cc2ed6 ("of/irq: Mark initialised interrupt controllers
as populated") the OF core flags interrupt controllers registered with the
IRQCHIP_DECLARE() macro as OF_POPULATED, so platform devices with the same
compatible string as the interrupt controller will not be registered.

This prevents the PMU platform device to be registered so the Exynos PMU
driver is never probed. This breaks (among other things) Suspend-to-RAM.

Fix this by clearing the OF_POPULATED flag in the PMU IRQ init callback,
to allow the Exynos PMU platform driver to be probed. The patch is based
on Philipp Zabel's "ARM: imx6: mark GPC node as not populated after irq
init to probe pm domain driver".

Fixes: 15cc2ed6 ("of/irq: Mark initialised interrupt controllers as populated")
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>