ocl: fixes and improvements #1409

Job	Run time
build-and-test (MPI=ON, OPENMP=ON, SMM=blas, openmpi)	10m 43s
build-on-cuda (OPENMP=ON)	15m 53s
build-on-opencl (OPENMP=ON, SMM=libxsmm)	11m 7s
build-and-test (MPI=ON, OPENMP=ON, SMM=blas, mpich)	6m 52s
build-and-test (MPI=ON, OPENMP=ON, SMM=libxsmm, openmpi)	9m 50s
build-and-test (MPI=ON, OPENMP=ON, SMM=libxsmm, mpich)	7m 56s
build-on-rocm (OPENMP=ON)	14m 34s
build-and-test (MPI=ON, OPENMP=OFF, SMM=blas, openmpi)	4m 46s
build-and-test (MPI=ON, OPENMP=OFF, SMM=blas, mpich)	4m 0s
pre-commit	1m 49s
build-and-test (MPI=ON, OPENMP=OFF, SMM=libxsmm, openmpi)	6m 26s
build-and-test (MPI=ON, OPENMP=OFF, SMM=libxsmm, mpich)	6m 26s
build-and-test (MPI=OFF, OPENMP=ON, SMM=blas, openmpi)	8m 38s
build-and-test (MPI=OFF, OPENMP=ON, SMM=libxsmm, openmpi)	8m 44s
build-and-test (MPI=OFF, OPENMP=OFF, SMM=blas, openmpi)	5m 22s
build-and-test (MPI=OFF, OPENMP=OFF, SMM=libxsmm, openmpi)	5m 8s
Combine & check coverage.	54s
	2h 9m 8s

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