aero: show all available cpu cores

If a device has more than one core, display all
cores and their respective frequencies.
While not only cores could have different frequency
values, a governor could be also (in theory) core-specific.

Since no one makes core based governors, this doesn't
need to be considered in future versuions.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
cpu: fix unnecessary warning

If the same governor was set, there was a warning
dialog for the user that the governor couldn't be
changed. Since one has to tap the governor specific
menu, this might be confusing for the user.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>