scripts/tags.sh: exclude tools directory from tags generation

scripts/tags.sh: exclude tools directory from tags generation

when COMPILED_SOURCE is set, running 'make ARCH=x86_64 COMPILED_SOURCE=1
cscope tags' in KBUILD_OUTPUT directory produces lots of "No such file
or directory" warnings:
...
realpath: sigchain.h: No such file or directory
realpath: orc_gen.c: No such file or directory
realpath: objtool.c: No such file or directory
...
let's exclude tools directory from tags generation

Fixes: 4f491bb6ea2a ("scripts/tags.sh: collect compiled source precisely")
Link: https://lore.kernel.org/lkml/20200809210056.GA1344537@thinkpad
Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Link: https://lore.kernel.org/r/20200810153650.1822316-1-rkovhaev@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>