xprtrdma: Remove unused function declaration rpcrdma_bc_post_recv()

rpcrdma_bc_post_recv() is never implemented since introduction in
commit f531a5db ("xprtrdma: Pre-allocate backward rpc_rqst and send/receive buffers").
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/xprt_rdma.h

@@ -593,7 +593,6 @@ void xprt_rdma_cleanup(void);
 int xprt_rdma_bc_setup(struct rpc_xprt *, unsigned int);
 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *);
 unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *);
-int rpcrdma_bc_post_recv(struct rpcrdma_xprt *, unsigned int);
 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *, struct rpcrdma_rep *);
 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst);
 void xprt_rdma_bc_free_rqst(struct rpc_rqst *);