IB/rxe: Fix rxe dev insertion to rxe_dev_list

The first argument of list_add_tail is the new item and the second
is the head of the list. Fix the code to pass arguments in the
right order, otherwise not all the rxe devices will be removed
during teardown.

Fixes: 8700e3e7 ('Soft RoCE driver')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Reviewed-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>