Review make.inc for MPI+GPU compilation

Using HPC SDK VERSION 21.2, CUDA_VERSION 11.0 and Intel MKL (see [cuda_env.sh.txt](https://github.com/QEF/q-e_schrodinger/files/6377242/cuda_env.sh.txt))

[make.inc.txt](https://github.com/QEF/q-e_schrodinger/files/6377254/make.inc.txt) is also attached.
