This patch adds support in SP_MIN to receive generic and
platform specific arguments from BL2.

The new signature is as following:
    void sp_min_early_platform_setup(void *from_bl2,
         void *plat_params_from_bl2);

ARM platforms have been modified to use this support.

Note: Platforms may break if using old signature.
      Default value for RESET_TO_SP_MIN is changed to 0.

Change-Id: I008d4b09fd3803c7b6231587ebf02a047bdba8d0