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