RDMA/qedr: remove set but not used variable 'ctx'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/infiniband/hw/qedr/verbs.c: In function 'qedr_create_srq':
drivers/infiniband/hw/qedr/verbs.c:1450:24: warning:
 variable 'ctx' set but not used [-Wunused-but-set-variable]

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Rahul Verma <rahul.verma@cavium.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>