rdma: Remove nes

This driver was first merged over 10 years ago and has not seen major
activity by the authors in the last 7 years. However, in that time it has
been patched 150 times to adapt it to changing kernel APIs.

Further, the hardware has several issues, like not supporting 64 bit DMA,
that make it rather uninteresting for use with modern systems and RDMA.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>