Now that this is only used in a few places in mr.c give it a sensible
name. It has nothing to do with the cache and can be invoked on any
MR. DMA is stopped and the user cannot touch the MR any further once it
completes.

Link: https://lore.kernel.org/r/20210304120745.1090751-5-leon@kernel.orgSigned-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>