RTC_CNTL_COCPU_SHUT_RESET_EN register was being reset during ULP RISC-V
initialization which does not let the ULP RISC-V coprocessor to reset
after it goes to halt. For proper operation of the coprocessor, it must
be reset after each cycle and hence this commit keeps
RTC_CNTL_COCPU_SHUT_RESET_EN set.