rdma UAPI: Use __kernel_sockaddr_storage

The kernel side is #ifdef'd to this type, and the UAPI header
should use it directly. It has slightly different alignment
requirments from the usual user space version.

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>