xprtrdma: Aggregate the inline settings in struct rpcrdma_ep

Clean up.

The inline settings are actually a characteristic of the endpoint,
and not related to the device. They are also modified after the
transport instance is created, so they do not belong in the cdata
structure either.

Lastly, let's use names that are more natural to RDMA than to NFS:
inline_write -> inline_send and inline_read -> inline_recv. The
/proc files retain their names to avoid breaking user space.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>