Fix names of new helper string to enum helper functions

[diptorupd]

std::string DDPL_StrToDeviceType(info::device_type devTy) The function name is incorrect. The function converts a device_type to a string, so should be DPPL_DeviceTypeToStr. Also, there is a typo in the prefix, should be DPPL and not DDPL.

info::device_type DPPL_DeviceTypeToStr(std::string devTyStr)Same as above, should be DPPL_StrToDeviceType.

Also, can we rename the directory to helper from details?