If copy_to_user() fails, it returns the number of bytes remaining to
be copied but we want to return a negative error code (-EFAULT) to the
user.

Fixes: 9d5dabfe ("drm/amdkfd: CRIU Save Shared Virtual Memory ranges")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Yat Sin <david.yatsin@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>