juno_ram: Re-initialize components upon power domain transitions

Some components within this module, such as PCI-e and
SMC, need to be re-initialized when their power domain
transitions to ON.

This patch enables the relevant logic through the use of
notifications from the `power_domain` module.

Change-Id: I7f63fae6470b98236989305a61971d617e4eeca8
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>