ftrace: allow trace_pipe to block on all reads

We expect things like "cat" to block on reads to trace_pipe. That's what
trace_pipe is for.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/trace/trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9197782..fd4ecc2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2231,8 +2231,6 @@
 	start = 0;
 
 	while (trace_empty(iter)) {
-		if (!(trace_flags & TRACE_ITER_BLOCK))
-			return -EWOULDBLOCK;
 		/*
 		 * This is a make-shift waitqueue. The reason we don't use
 		 * an actual wait queue is because: