Begin transition to fiptool

ARM-TF is removing fip_create and replacing it with fiptool.

Rather than move directly to fiptool, make some mods to how we use
fip_create so that the minimal changes will work with the new fip_create
wrapper script but also with the existing fip_create executable.

Change-Id: Ic5746e94d2aa665926ea852c88338c02846420f5
Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>