pNFS: Fix assignment of xprtdata.cred

The comma at the end of the line was leftover from an earlier refactor
of the _nfs4_pnfs_v3_ds_connect() function. This is technically valid C,
so the compilers didn't catch it, but if I'm understanding how it works
correctly it assigns the return value of rpc_clnt_add_xprtr() to
xprtdata.cred.

Reported-by: Olga Kornievskaia <[e-mail]>
Fixes: a12f996d3413 ("NFSv4/pNFS: Use connections to a DS that are all of the same protocol family")
Signed-off-by: Anna Schumaker <[e-mail]>

fs/nfs/pnfs_nfs.c

···
 			* Test this address for session trunking and
 			* add as an alias
 			*/
-			xprtdata.cred = nfs4_get_clid_cred(clp),
+			xprtdata.cred = nfs4_get_clid_cred(clp);
 			rpc_clnt_add_xprt(clp->cl_rpcclient, &xprt_args,
 					  rpc_clnt_setup_test_and_add_xprt,
 					  &rpcdata);