drm/amdkfd: CRIU allow external mm for svm ranges

Both svm_range_get_attr and svm_range_set_attr helpers use mm struct
from current but for a Checkpoint or Restore operation, the current->mm
will fetch the mm for the CRIU master process. So modify these helpers to
accept the task mm for a target kfd process to support Checkpoint
Restore.

Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>