ib_{uverbs/core}: add new ib_create_qp_ex with udata arg

ib_{uverbs/core}: add new ib_create_qp_ex with udata arg

Necessary to get device specific arguments through to XRC QPs.
Added new local header file to serve as support interface
between ib_core and ib_uverbs.

Right now there is a lot of duplicate setup code in uverbs_cmd.c
on the ib_uverbs side and verbs.c on the ib_core side. This commit
is a quick fix to have XRC support working, but similar calls
can be added to consolidate the code for other parts of the API.

Orabug: 20930262

Signed-off-by: Knut Omang <knut.omang@oracle.com>
Signed-off-by: Mukesh Kacker <mukesh.kacker@oracle.com>