livibverbs: Add support for XRC SRQs

XRC support requires the use of a new type of SRQ.

XRC shared receive queues: xrc srq's are similar to normal
srq's, except that they are bound to an xrcd, rather
than to a protection domain.  Based on the current spec
and implementation, they are only usable with xrc qps.  To
support xrc srq's, we define a new srq_init_attr structure
to include an srq type and other needed information.

The kernel ABI is also updated to allow creating extended
SRQs.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>