Remove -Mchkfpstk flag from cmake/NVHPC.cmake

[cponder]

The -Mchkfpstk flag here

5    set(check_all "-Mbounds -Mchkfpstk -Mchkstk")

causes an error

nvfortran-Error-Unknown switch: -Mchkfpstk

I assume that it's an old flag no longer supported.

[cponder]

A workaround is to add the -noswitcherror, which is usually used to make the PGI compilers digest GCC or Intel flags.
But I'd prefer to just clean it out.