RDMA/core: Fix user CQ creation for drivers without create_cq

RDMA/core: Fix user CQ creation for drivers without create_cq

CQ creation is failing for drivers that only implement create_user_cq
(e.g. EFA), when buffer isn't provided by userspace. This because of a
leftover check that requires create_cq existence in such case.

Remove the create_cq existence check from the no-buffer path. The
buffer is optional and drivers that handle their own memory should work
through create_user_cq regardless.

Fixes: 584ec74748e6 ("RDMA/core: Prepare create CQ path for API unification")
Link: https://patch.msgid.link/r/20260416201408.13980-1-mrgolin@amazon.com
Signed-off-by: Michael Margolin <mrgolin@amazon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>