IB/IPoIB: Separate control and data related initializations

This patch prepares init and teardown flows so we can call them
through ipoib_options function pointers.

It arranges that area of code as the following:
 * All operations which deal with the resource allocation/deletion
   are performed in one place.
 * All operations that are control oriented, meaning that they are not
   connected to a specific hardware, are performed in a separate place.

The operations for allocation of hardware resources are now in the
function ipoib_dev_init_default, and the deletion of all the resources
are in ipoib_dev_uninit_default

The only exception is the creation of the PD object,
which is used both for resource allocation (create QP etc.)
and for control flows like creating AH.

It also does:
 * Move creation of rx_ring and tx_ring to be in the resources
   allocation area.
 * Move the function ipoib_ib_dev_open that does the open device
   to the control area instead of the dev_init which creates resources.

Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Reviewed-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>