[ROCm] Replace HIP_PATH with ROCM_PATH for rocm 6.0

In preparation for the upcoming 6.0 release, this commit replaces the HIP_PATH cmake cache variable with a new cache variable ROCM_PATH to reflect changes in the ROCm directory structure: https://rocm.docs.amd.com/en/docs-5.3.3/understand/file_reorg.html By default, ROCM_PATH points at the root of the ROCm installation (e.g. /opt/rocm).