sched, net: Clean up preempt_enable_no_resched() abuse

The only valid use of preempt_enable_no_resched() is if the very next
line is schedule() or if we know preemption cannot actually be enabled
by that statement due to known more preempt_count 'refs'.

Reviewed-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Peter Zijlstra <[e-mail]>
Cc: [e-mail]
Cc: Eliezer Tamir <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: Mike Galbraith <[e-mail]>
Cc: [e-mail]
Cc: Arjan van de Ven <[e-mail]>
Cc: [e-mail]
Cc: Linus Torvalds <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

net/ipv4/tcp.c

···
 		    (len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&
 		    !sysctl_tcp_low_latency &&
 		    net_dma_find_channel()) {
-			preempt_enable_no_resched();
+			preempt_enable();
 			tp->ucopy.pinned_list =
 					dma_pin_iovec_pages(msg->msg_iov, len);
 		} else {
-			preempt_enable_no_resched();
+			preempt_enable();
 		}
 	}
 #endif