Add Support for AMD Navi Gaming Cards

[pbauman]

Some folks over at mfem/mfem#2910 are trying to run with HYPRE on a Navi gaming card. The issue is that the Navi cards run with warp/wavefront size 32 and not 64. Currently, AMD GPU support in HYPRE assumes wavefront size 64. The steps I see to address this are as follows:

1. Use rocm_agent_enumerator to get the gfxarch from the system if the user doesn't set it with --gpu-arch
2. Need to do some string parsing to decide whether gfx is 9XY or 10XY
3. Based on the above, can set a preprocessing variable to denote wavefront size
4. Update device_utils.h accordingly

I will try to get to this soonish (I have a few other fires to put out first).