mod_scmi_power_domain: Add debug support for set/get_enabled

If supported by platform, change the pd state with help
from debug module's set/get_enabled calls

Change-Id: I2c766ab36f6f0232db6605848cd3518706152df4
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
Signed-off-by: Raphael Gault <raphael.gault@arm.com>
Signed-off-by: Girish Pathak <girish.pathak@arm.com>