This commit fixes a bug wherein an incorrect bit-width of 0 was being
used while reading the RTC_CNTL_LOW_POWER_ST_REG in ulp_fsm example code
while judging whether the system is ready for wakeup. The correct value
should be a bit-width of 1 to read bit#27 (RTC_CNTL_MAIN_STATE_IDLE) of
the RTC_CNTL_LOW_POWER_ST_REG register on esp32.