When some GPUs don't support SVM, don't disabe it for the entire process.
That would be inconsistent with the information the process got from the
topology, which indicates SVM support per GPU.

Instead disable SVM support only for the unsupported GPUs. This is done
by checking any per-device attributes against the bitmap of supported
GPUs. Also use the supported GPU bitmap to initialize access bitmaps for
new SVM address ranges.

Don't handle recoverable page faults from unsupported GPUs. (I don't
think there will be unsupported GPUs that can generate recoverable page
faults. But better safe than sorry.)
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Philip Yang <philip.yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>