amdkfd: process svm ioctl only on the primary kfd process

amdkfd: process svm ioctl only on the primary kfd process

svm ioctl should only be processed on the primary
kfd process because only the lifecycle of the
primary kfd process is tied to the  user space
applicaiton.

Another reason is in virtualization the hypervisor owns
the primary kfd process as a privileged one.

Signed-off-by: Zhu Lingshan <lingshan.zhu@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>