s6lx9_microboard_defconfig: lock kernel version

Fixes https://travis-ci.org/buildroot/buildroot-defconfig-testing/jobs/123187960

The defconfig broke after we moved the default kernel version to 4.5.x. Fix
it by locking the kernel version in the defconfig.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
1 file changed