patman: README documentation nits (unit test)

adjust instructions for the invocation of Patman's self test: the -t
flag appears to have a different meaning now, refer to the --test option
for the builtin unit test; adjust a directory location and make sure to
run the file which resides in the source directory

Signed-off-by: Gerhard Sittig <gsi@denx.de>
Acked-by: Simon Glass <sjg@chromium.org>

Author: Gerhard Sittig

tools/patman/README

@@ -452,12 +452,12 @@ Most of these are indicated by a TODO in the code.
 
 It would be nice if this could handle the In-reply-to side of things.
 
-The tests are incomplete, as is customary. Use the -t flag to run them,
-and make sure you are in the tools/scripts/patman directory first:
+The tests are incomplete, as is customary. Use the --test flag to run them,
+and make sure you are in the tools/patman directory first:
 
     $ cd /path/to/u-boot
-    $ cd tools/scripts/patman
-    $ patman -t
+    $ cd tools/patman
+    $ ./patman --test
 
 Error handling doesn't always produce friendly error messages - e.g.
 putting an incorrect tag in a commit may provide a confusing message.