net/tls: remove set but not used variables

Commit 4504ab0 ("net/tls: Inform user space about send buffer availability")
made us report write_space regardless whether partial record
push was successful or not.  Remove the now unused return value
to clean up the following W=1 warning:

net/tls/tls_device.c: In function ‘tls_device_write_space’:
net/tls/tls_device.c:546:6: warning: variable ‘rc’ set but not used [-Wunused-but-set-variable]
  int rc = 0;
      ^~

CC: Vakul Garg <vakul.garg@nxp.com>
CC: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/tls_device.c

@@ -541,14 +541,11 @@ static int tls_device_push_pending_record(struct sock *sk, int flags)
 
 void tls_device_write_space(struct sock *sk, struct tls_context *ctx)
 {
-	int rc = 0;
-
 	if (!sk->sk_write_pending && tls_is_partially_sent_record(ctx)) {
 		gfp_t sk_allocation = sk->sk_allocation;
 
 		sk->sk_allocation = GFP_ATOMIC;
-		rc = tls_push_partial_record(sk, ctx,
-					     MSG_DONTWAIT | MSG_NOSIGNAL);
+		tls_push_partial_record(sk, ctx, MSG_DONTWAIT | MSG_NOSIGNAL);
 		sk->sk_allocation = sk_allocation;
 	}
 }