Convert the collision-retry lock around hmm_range_fault to use the one now
provided by the mmu_interval notifier.

Although this driver does not seem to use the collision retry lock that
hmm provides correctly, it can still be converted over to use the
mmu_interval_notifier api instead of hmm_mirror without too much trouble.

This also deletes another place where a driver is associating additional
data (struct amdgpu_mn) with a mmu_struct.

Link: https://lore.kernel.org/r/20191112202231.3856-13-jgg@ziepe.caSigned-off-by: NPhilip Yang <Philip.Yang@amd.com>
Reviewed-by: NPhilip Yang <Philip.Yang@amd.com>
Tested-by: NPhilip Yang <Philip.Yang@amd.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>