sched/fair: remove capacity tracking from energy_diff

In preparation for the energy_diff refactoring, let's remove all the
SchedTune specific bits which are used to keep track of the capacity
variations requited by the PESpace filtering.

This removes also the energy_normalization function and the wrapper of
energy_diff which is used to trigger a PESpace filtering by
schedtune_accept_deltas().

The remaining code is the "original" energy_diff function which
looks just at the energy variations to compare prev_cpu vs next_cpu.

Change-Id: I4fb1d1c5ba45a364e6db9ab8044969349aba0307
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>