NFSD: Remove open coding of string copy

Instead of open coding a __dynamic_array(), use the __string() and
__assign_str() helper macros that exist for this kind of use case.

Part of an effort to remove deprecated strlcpy() [1] completely from the
kernel[2].

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Fixes: 3c92fba ("NFSD: Enhance the nfsd_cb_setup tracepoint")
Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/trace.h

@@ -1365,19 +1365,19 @@ TRACE_EVENT(nfsd_cb_setup,
 		__field(u32, cl_id)
 		__field(unsigned long, authflavor)
 		__sockaddr(addr, clp->cl_cb_conn.cb_addrlen)
-		__array(unsigned char, netid, 8)
+		__string(netid, netid)
 	),
 	TP_fast_assign(
 		__entry->cl_boot = clp->cl_clientid.cl_boot;
 		__entry->cl_id = clp->cl_clientid.cl_id;
-		strlcpy(__entry->netid, netid, sizeof(__entry->netid));
+		__assign_str(netid, netid);
 		__entry->authflavor = authflavor;
 		__assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
 				  clp->cl_cb_conn.cb_addrlen)
 	),
 	TP_printk("addr=%pISpc client %08x:%08x proto=%s flavor=%s",
 		__get_sockaddr(addr), __entry->cl_boot, __entry->cl_id,
-		__entry->netid, show_nfsd_authflavor(__entry->authflavor))
+		__get_str(netid), show_nfsd_authflavor(__entry->authflavor))
 );
 
 TRACE_EVENT(nfsd_cb_setup_err,