IB/mlx5: Remove superfluous include of io-mapping.h

This file does not use any structs or functions defined by io-mapping.h
(nor does it directly use iomap, ioremap, iounamp or friends). Remove it
to simplify verification of changes to io-mapping.h

The include existed since its inception in

commit e126ba97
Author: Eli Cohen <eli@mellanox.com>
Date:   Sun Jul 7 17:25:49 2013 +0300

    mlx5: Add driver for Mellanox Connect-IB adapters

which looks like a copy across from the Mellanox ethernet driver.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Eli Cohen <eli@mellanox.com>
Cc: Jack Morgenstein <jackm@dev.mellanox.co.il>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Matan Barak <matanb@mellanox.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
Cc: linux-rdma@vger.kernel.org
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Tested-by: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>