checkkconfigsymbols.py: filter reports for tools/

Recent changes to the build system of tools suggest to filter reports
for the entire tools directory.  Various C preprocessor identifiers are
prefixed with CONFIG_ but are NOT defined in Kconfig but in Makefiles in
the tools directory.  Such identifiers are false positives for most static
analysis tools (i.e., scripts/checkkconfigsymbols.py) since the CONFIG_
prefix and the _MODULE suffix is reserved for Kconfig features in CPP
and Make syntax.

Signed-off-by: Valentin Rothberg <Valentin.Rothberg@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>