RDMA/uverbs: Properly check command supported mask

The check based on index is not sufficient because

  IB_USER_VERBS_EX_CMD_CREATE_CQ = IB_USER_VERBS_CMD_CREATE_CQ

and IB_USER_VERBS_CMD_CREATE_CQ <= IB_USER_VERBS_CMD_OPEN_QP,
so if we execute IB_USER_VERBS_EX_CMD_CREATE_CQ this code checks
ib_dev->uverbs_cmd_mask not ib_dev->uverbs_ex_cmd_mask.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>