uboot-phytec

patman: Format checkpatch messages for IDE throwback

It is convenient to be able to deal with checkpatch warnings in the same
way as build warnings. Tools such as emacs and kate can quickly locate
the source file and line automatically.

To achieve this, adjust the format to match the C compiler, and output to
stderr.

Signed-off-by: Simon Glass <sjg@chromium.org>