drivers: counter: fix mcux lptmr unit test issue.

The counter alarm irq shall set the match value
to the max top value after stopping the timer, otherwise
the next start of the lptmr counter may shortly match the
the previous match value thus cause test_valid_function_without_alarm
run failed.

Signed-off-by: Holt Sun <holt.sun@nxp.com>

Author: Holt-Sun

drivers/counter/counter_mcux_lptmr.c

@@ -247,6 +247,7 @@ static void mcux_lptmr_isr(const struct device *dev)
 		uint32_t current_count = LPTMR_GetCurrentTimerCount(config->base);
 
 		LPTMR_StopTimer(config->base);
+		LPTMR_SetTimerPeriod(config->base, config->info.max_top_value);
 
 		callback(dev, 0, current_count, user_data);