scripts: update checkpatch.pl to latest upstream version

Update to v3.14-rc4's version of checkpatch.pl.  In doing so we drop the
changes to top_of_kernel_tree() as we pass in --no-tree and drop our
changes about MAINTAINERS as that's for reporting checkpatch.pl problems
itself (and upstream has said they'll reword this section to be
clearer).

Signed-off-by: Tom Rini <trini@ti.com>