ARM platform changes for new version of image loading

ARM platform changes for new version of image loading

This patch adds changes in ARM platform code to use new
version of image loading.

Following are the major changes:
  -Refactor the signatures for bl31_early_platform_setup()
   and arm_bl31_early_platform_setup() function to use
   `void *` instead of `bl31_params_t *`.
  -Introduce `plat_arm_bl2_handle_scp_bl2()` to handle
   loading of SCP_BL2 image from BL2.
  -Remove usage of reserve_mem() function from
   `arm_bl1_early_platform_setup()`
  -Extract BL32 & BL33 entrypoint info, from the link list
   passed by BL2, in `arm_bl31_early_platform_setup()`
  -Provides weak definitions for following platform functions:
     plat_get_bl_image_load_info
     plat_get_next_bl_params
     plat_flush_next_bl_params
     bl2_plat_handle_post_image_load
  -Instantiates a descriptor array for ARM platforms
   describing image and entrypoint information for
   `SCP_BL2`, `BL31`, `BL32` and `BL33` images.

All the above changes are conditionally compiled using the
`LOAD_IMAGE_V2` flag.

Change-Id: I5e88b9785a3df1a2b2bbbb37d85b8e353ca61049