perf debug: fix hex dump partial final line

The loop counter math in trace_event was much more complicated than
necessary, resulting in incorrectly decoding the human-readable
portion of the partial last line of hexdump in "perf trace -D" output:

.  0020:  00 00 00 00 00 00 00 00 2f 73 62 69 6e 2f 69 6e  ......../sbin/i
.  0030:  69 74 00 00 00 00 00 00                          /sbin/i

With this fixed (and simpler!) code, we get the correct output:

.  0020:  00 00 00 00 00 00 00 00 2f 73 62 69 6e 2f 69 6e  ......../sbin/in
.  0030:  69 74 00 00 00 00 00 00                          it......

Cc: Ingo Molnar <mingo@elte.hu>
LPU-Reference: <20100612024404.GA24469@hexapodia.org>
Signed-off-by: Andy Isaacson <adi@hexapodia.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/debug.c

@@ -86,12 +86,10 @@ void trace_event(event_t *event)
 			dump_printf_color("  ", color);
 			for (j = 0; j < 15-(i & 15); j++)
 				dump_printf_color("   ", color);
-			for (j = 0; j < (i & 15); j++) {
-				if (isprint(raw_event[i-15+j]))
+			for (j = i & ~15; j <= i; j++) {
 				dump_printf_color("%c", color,
-							  raw_event[i-15+j]);
-				else
-					dump_printf_color(".", color);
+						isprint(raw_event[j]) ?
+						raw_event[j] : '.');
 			}
 			dump_printf_color("\n", color);
 		}