platform/x86: intel_atomisp2_pm: Refactor timeout loop

The timeout loop look more naturally when done like

	unsigned long timeout = ...;
	...
	do {
		...
		if (cond)
			return %OK;

		sleep(...);
	} while (time_before(timeout));

	...print timeout error...
	return %ERROR;

It also saves LOCs. Convert the driver to this format of timeout loop.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>