RDMA/core: Get rid of ib_create_qp_user

This function accepts a udata but does nothing with it, and is never
passed a !NULL udata. Rename it to ib_create_qp which was the only caller
and remove the udata.

Link: https://lore.kernel.org/r/20200213191911.GA9898@ziepe.ca


Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>