drivers: dai: dmic: do not call k_sleep() in PM callbacks

The call to k_sleep() is not safe as dai_dmic_probe() is called
from PM dmic_pm_action() and k_can_yield() may be false.

Problem was caught on Intel WCL ADSP platform with SOF as application
and a Zephyr build with asserts enabled.

Fix the issue by using k_busy_wait() instead.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>