Support ROCm 7.0

[MarcelKoch]

The current version of Ginkgo doesn't build with ROCm 7.0 as reported in hypre-space/hypre#1343.
The cause is that warpSize isn't a compile-time constant anymore, see: https://rocm.docs.amd.com/projects/HIP/en/latest/how-to/hip_cpp_language_extensions.html#warpsize

[upsj]

Seems like a duplicate of #1429, since the fix for that would also fix this issue.

[MarcelKoch]

I guess this is a slightly bigger issue, since Ginkgo won't compile with ROCm 7.0 for any GPU architecture.

[upsj]

There's the quick fix (hard-coding it to 64) and then the full fix (#1429)