drm/amdkfd: handle svm migrate init error

If svm migration init failed to create pgmap for device memory, set
pgmap type to 0 to disable device SVM support capability.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>