RDMA/include: Replace license text with SPDX tags

The header files in RDMA subsystem are dual licensed and can be
described by simple SPDX tag, so replace all of them at once
together with making them use the same coding style for header
guard defines.

Link: https://lore.kernel.org/r/20200719072521.135260-1-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>