The PM API can be used in many places. So, It is difficult to check CONFIG_PM in all codes. Therefore, even if CONFIG_PM is disabled, we change it so that the API can be provided as follows.
the PM driver is always enabled,
when CONFIG_PM is disabled, pm_sleep(milliseconds) is replaced with usleep(milliseconds * USEC_PER_MSEC).
The PM API can be used in many places. So, It is difficult to check CONFIG_PM in all codes. Therefore, even if CONFIG_PM is disabled, we change it so that the API can be provided as follows.