build: Add script to generate extra images

Change-Id: I53081c7a2b4f18bc8c8a27b04d311a6b078b2022

Use CM standard qcom naming

Change-Id: I360b3dcf1fe82140a7993189e881f9d77b571bef

generate_extra_images: Remove deprecated image generation

* Remove msm7x27a/msm7x30 nand images
* Remove msm8930 1G userdata

Change-Id: I81b93d34893d504a53f2aadb9c3ac2089c06860c

generate_extra_images: Rename targets and add 'sec' prefix

Change-Id: Ie7debfb33349d16d9a457ff817072af2f3a10c0f