Added some missing conversions to the Half class, and fixed the implementation of the < operator on cuda devices.
Added some missing conversions to the Half class, and fixed the implementation of the < operator on cuda devices.

ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,pasuka/eigen,pasuka/eigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,pasuka/eigen,ritsu1228/eigen