firmware: exynos-acpm: use ktime APIs for timeout detection

firmware: exynos-acpm: use ktime APIs for timeout detection

acpm_dequeue_by_polling() uses a loop counter and assumes that each
iteration of the loop takes 20us. It may take longer, though, because
usleep_range() may sleep a different amount.

Switch to using ktime_get() / ktime_before() to detect the timeout
condition more reliably.

This change also makes the code easier to follow and it allows us to
adjust the sleep if necessary, without having to adjust the loop
counter exit condition.

Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20250325-acpm-atomic-v3-1-c66aae7df925@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>