PM: EM: Refactor struct em_perf_domain and add default_table

The Energy Model support runtime modifications. Refactor old
implementation which accessed struct em_perf_state and introduce
em_perf_domain::default_table to clean up the design. This new field
is better aligned with em_perf_domain::runtime_table and helps to
distinguish them better.

Update all drivers or frameworks which used the old field:
em_perf_domain::table and now should use em_perf_domain::default_table.

Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>