minor tweaks

Explicitly enable or disable KOKKOS support, as provided by the KOKKOS

package.  Even if LAMMPS is built with this package, as described

in "Speed kokkos"_Speed_kokkos.html, this switch must be set to enable

running with the KOKKOS-enabled styles the package provides.  If the

running with KOKKOS-enabled styles the package provides.  If the

switch is not set (the default), LAMMPS will operate as if the KOKKOS

package were not installed; i.e. you can run standard LAMMPS or with

the GPU or USER-OMP packages, for testing or benchmarking purposes.

[-suffix style args] :link(suffix)

Use variants of various styles if they exist.  The specified style can

be {cuda}, {gpu}, {intel}, {kk}, {omp}, {opt}, or {hybrid}.  These

be {gpu}, {intel}, {kk}, {omp}, {opt}, or {hybrid}.  These

refer to optional packages that LAMMPS can be built with, as described

in "Accelerate performance"_Speed.html.  The "gpu" style corresponds to the

GPU package, the "intel" style to the USER-INTEL package, the "kk"