sid: Move to an always available interface

Remove the need to bind to the sid module interface. This enables access
to the system information data during the initialization stage of the
pre-runtime phase. This way, configuration data can be tuned according
to system information data.

Change-Id: I2e9e37d562af0d7f6a8ba844a79a78f823f6a64a
Signed-off-by: Ronald Cron <ronald.cron@arm.com>