IB: directly cast the sockaddr union to aockaddr

Like commit 641114d2af31 ("RDMA: Directly cast the sockaddr union to
sockaddr") we need to quiet gcc 9 from warning about this crazy union.
That commit did not fix all of the warnings in 4.19 and older kernels
because the logic in roce_resolve_route_from_path() was rewritten
between 4.19 and 5.2 when that change happened.

Cc: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>