RDMA/core: Move legacy MAD IOCTL declarations to common file

Move legacy MAD IOCTL declarations to rdma_user_ioctl.h file.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>