fix(cpus): check for SME presence in Gelas

The original powerdown function for Gelas included SME disabling
instructions but did not check for the presence of SME before disabling.
This could lead to unexpected beaviors. This patch adds that check so
the feature is disabled only if it is present.

Change-Id: I582db53a6669317620e4f72a3eac87525897d3d0
Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
2 files changed