cpufrequtils: Remove SERVICES entry for this package - fixes Bug#12933

cpufrequtils: Remove SERVICES entry for this package - fixes Bug#12933

- cpufrequtils is a set of "tools" to manage and set cpu freq settings.
- There is an initscript but this is only loading the cpu dependent kernel modules that
   are required by cpufrequtils.
- Therefore cpufrequtils is not a service but a set of tools that are used when required.
- SERVICES line made blank so that this addon does not show up in the services addon table.
- Modified install initscript line to not use SERVICES variable

Fixes: Bug#12933
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Bernhard Bitsch <bbitsch@ipfire.org>