Update fip_create params for ARM-TF pull req 479

While ARM-TF v1.2 changed the params of fip_create and cert_create as
per commit "Fix for ARM-TF v1.2" (b7d86b98), pull request #479 [1]
updates fip_create to use the same params as cert_create.

This commit updated the script to match the new fip_create params.

[1] https://github.com/ARM-software/arm-trusted-firmware/pull/479


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