Move set_reg_umr_segment() and its helpers to umr.c.

Link: https://lore.kernel.org/r/5a7fac8ae8543521d19d174663245ae84b910310.1649747695.git.leonro@nvidia.comSigned-off-by: Aharon Landau <aharonl@nvidia.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>