Refactor config files

There are many things in configuration files which will need to be
re-used across platforms in future but configured from specific file
currently which can result into duplicate code, so refactoring is
needed.

To do that, This patch adds android.config file to manage android loading
to ram and modifying bootargs for android boot according to build
configuration.

This patch also adds customize.config which can customize bootargs, compiler
flags etc based on platform specific config. In future, If customization
code is big enough than separate config file can be created similar to
android.config, for small customization, customize.config can be
utilized directly.

Signed-off-by: Jagdish Gediya <jagdish.gediya@arm.com>