nfs[23] tcp breakage in mount with binary options

We forget to set nfs_server.protocol in tcp case when old-style binary
options are passed to mount.  The thing remains zero and never validated
afterwards.  As the result, we hit BUG in fs/nfs/client.c:588.

Breakage has been introduced in NFS: Add nfs_alloc_parsed_mount_data
merged yesterday...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>