infiniband: fix race condition between infiniband mlx4, mlx5 driver and core dumping

This patch is the extension of following upstream commit to fix
the race condition between get_task_mm() and core dumping
for IB->mlx4 and IB->mlx5 drivers:

commit 04f5866e41fb ("coredump: fix race condition between
mmget_not_zero()/get_task_mm() and core dumping")'

Thanks to Jason for pointing this.

Signed-off-by: Ajay Kaher <akaher@vmware.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>