Unified CUDA and OpenCL struc fields of int/int* type

1. gmx_gpu_info_t
replaced: ncuda_dev, nocl_dev
by:  n_dev
replaced: ncuda_dev_compatible, nocl_dev_compatible
by: n_dev_compatible

2. gmx_gpu_opt_t
replaced: ncuda_dev_use, nocl_dev_use
by: n_dev_use
replaced: cuda_dev_use, ocl_dev_use
by: dev_use