NFSv4.2: Remove ifdef CONFIG_NFSD from NFSv4.2 client SSC code.

The client SSC code should not depend on any of the CONFIG_NFSD config.
This patch removes all CONFIG_NFSD from NFSv4.2 client SSC code and
simplifies the config of CONFIG_NFS_V4_2_SSC_HELPER, NFSD_V4_2_INTER_SSC.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>