firmware: exynos-acpm: allow use during system shutdown

firmware: exynos-acpm: allow use during system shutdown

We need to access the PMIC during late system shutdown and at that time
we are not allowed to sleep anymore.

To make this case work, and since we can't detect this case in a
non-racy way, switch to using udelay() unconditionally, instead of
usleep_range().

Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20250325-acpm-atomic-v3-2-c66aae7df925@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>