IB/uverbs: Fix alignment of struct ib_uverbs_create_qp_resp

The size of struct ib_uverbs_create_qp_resp is not even multiple of 8
bytes.  This causes problems for low-level drivers that add private
data after the structure: 32-bit userspace will look in the wrong
place for a response from a 64-bit kernel.  Fix this by adding a
reserved field.  Also, bump the ABI version because this changes the
size of a structure.

Pointed out by Hoang-Nam Nguyen <HNGUYEN@de.ibm.com>.

Signed-off-by: Roland Dreier <rolandd@cisco.com>