In release builds, the Trusty SPD fails to build because of an unused
variable. Note that this warning message doesn't show in debug builds
because INFO() messages are not compiled out like in release mode.

This patch fixes this issue by removing this variable and using its
value in place directly in the INFO() macro call.

Change-Id: I1f552421181a09412315eef4eaca586012022018
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>