fip: extend fip module to accept custom uuid through module config

fiptool allows packaging images as a blob with custom UUID but
fip module in SCP does not allow platform to use custom UUIDs for images.
Current workaround that is being used is to add a custom entry in fip.h
and make appropriate changes elsewhere in common fip module.
This approach is not scalable and requires changes in common code.

This patch adds changes to support platforms to use custom UUIDs
through config_fip.c file. Platforms can add any number of custom
entries through config which is then parsed by fip module.

Signed-off-by: sahil <sahil@arm.com>
Change-Id: I4c0770f9d053e3bbcafa959a1bc83c4175f32c06