Test and remove `QUDA_ENABLE_P2P=7` default if possible

[maddyscientist]

With the fixes to UCX regarding its inability to deal with reused CUDA IPC memory handles (openucx/ucx#3192) we should be able to remove the default behaviour QUDA_ENABLE_P2P=7 which essentially forbids CUDA-aware IPC and regular IPC communications policies being used in the same run. This is a reminder to me to test that this is true and if so, remove this work around.