PM: EM: Change debugfs configuration to use runtime EM table data

Dump the runtime EM table values which can be modified in time. In order
to do that allocate chunk of debug memory which can be later freed
automatically thanks to devm_kcalloc().

This design can handle the fact that the EM table memory can change
after EM update, so debug code cannot use the pointer from initialization
phase.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>