IB/core: Resolve Ethernet L2 addresses when modifying QP

Existing user space applications provide only IBoE L3 address
attributes to the kernel when they issue a modify QP modify.  To work
with them and let such apps (plus kernel consumers which don't use the
RDMA-CM) keep working transparently under the IBoE GID IP addressing
changes, add an Eth L2 address resolution helper.

Signed-off-by: Moni Shoua <monis@mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

diff --cc drivers/infiniband/core/core_priv.h
Simple merge

diff --cc drivers/infiniband/core/uverbs_cmd.c
Simple merge

diff --cc drivers/infiniband/core/verbs.c
Simple merge