[PATCH] docs: fix wrong usage of proftool

[Puhan Zhou]

The usage of proftool in docs is incorrect. If proftool is used without
'-o' argument, it will show the usage like following

$ ./sandbox/tools/proftool -m sandbox/System.map -t trace -f funcgraph dump-ftrace >trace.dat
Must provide trace data, System.map file and output file
Usage: proftool [-cmtv] <cmd> <profdata>

Change '>' to '-o' to fix it.

Signed-off-by: Puhan Zhou <puh4n.zhou at gmail.com>
---
 doc/develop/trace.rst | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/doc/develop/trace.rst b/doc/develop/trace.rst
index 9bbe1345d2..546862020b 100644
--- a/doc/develop/trace.rst
+++ b/doc/develop/trace.rst
@@ -139,7 +139,7 @@ There is a -f option available to select a function graph:
 
 .. code-block:: console
 
-    $ ./sandbox/tools/proftool -m sandbox/System.map -t trace -f funcgraph dump-ftrace >trace.dat
+    $ ./sandbox/tools/proftool -m sandbox/System.map -t trace -f funcgraph dump-ftrace -o trace.dat
 
 Again, you can use kernelshark or trace-cmd to look at the output. In this case
 you will see the time taken by each function shown against its exit record.
@@ -171,7 +171,7 @@ command:
 
 .. code-block:: console
 
-    $ ./sandbox/tools/proftool -m sandbox/System.map -t trace dump-flamegraph >trace.fg
+    $ ./sandbox/tools/proftool -m sandbox/System.map -t trace dump-flamegraph -o trace.fg
     $ flamegraph.pl trace.fg >trace.svg
 
 You can load the .svg file into a viewer. If you use Chrome (and some other
@@ -191,7 +191,7 @@ spend in each call stack:
 
 .. code-block:: console
 
-    $ ./sandbox/tools/proftool -m sandbox/System.map -t trace dump-flamegraph -f timing >trace.fg
+    $ ./sandbox/tools/proftool -m sandbox/System.map -t trace dump-flamegraph -f timing -o trace.fg
     $ flamegraph.pl trace.fg >trace.svg
 
 Note that trace collection does slow down execution so the timings will be
-- 
2.34.1