regulator: core: Prevent integer underflow

By using a ratio of delay to poll_enabled_time that is not integer
time_remaining underflows and does not exit the loop as expected.
As delay could be derived from DT and poll_enabled_time is defined
in the driver this can easily happen.

Use a signed iterator to make sure that the loop exits once
the remaining time is negative.
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Link: https://lore.kernel.org/r/20220909125954.577669-1-patrick.rudolph@9elements.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -2699,7 +2699,7 @@ static int _regulator_do_enable(struct regulator_dev *rdev)
 	 * return -ETIMEDOUT.
 	 */
 	if (rdev->desc->poll_enabled_time) {
-		unsigned int time_remaining = delay;
+		int time_remaining = delay;
 
 		while (time_remaining > 0) {
 			_regulator_delay_helper(rdev->desc->poll_enabled_time);