test_kmod: fix kmod.sh by making it executable

We had just forgotten to do this. Without this if we run the
following we get a permission denied:

sudo make -C tools/testing/selftests/kmod/ run_tests
make: Entering directory '/home/mcgrof/linux-next/tools/testing/selftests/kmod'
/bin/sh: ./kmod.sh: Permission denied
selftests:  kmod.sh [FAIL]
/home/mcgrof/linux-next/tools/testing/selftests/kmod
make: Leaving directory '/home/mcgrof/linux-next/tools/testing/selftests/kmod

Fixes: 39258f448d71 ("kmod: add test driver to stress test the module loader")
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>