power: support both interactive and ondemand

Adapted from S5PC110 PowerHAL.

Signed-off-by: David Rodero <david@codiguiel.net>

Conflicts:
	power/power_latona.c

Change-Id: Ife363b1117237cdb48b1b039f3e01ed711ae5a06
Signed-off-by: David Rodero <david@codiguiel.net>