Further renames of platform porting functions ...

Rename the ic_* platform porting functions to plat_ic_* to be
consistent with the other functions in platform.h. Also rename
bl31_get_next_image_info() to bl31_plat_get_next_image_ep_info()
and remove the duplicate declaration in bl31.h.

Change-Id: I4851842069d3cff14c0a468daacc0a891a7ede84

Remove FVP specific comments in platform.h ...

Remove the FVP specific comments in platform.h since this file
is re-usable across all platforms.

Change-Id: Ifd4a4f72562adb3ecf8b9078b0150f170ef22dba

Add enable mmu platform porting interfaces ...

Previously, the enable_mmu_elX() functions were implicitly part of
the platform porting layer since they were included by generic
code. These functions have been placed behind 2 new platform
functions, bl31_plat_enable_mmu() and bl32_plat_enable_mmu().
These are weakly defined so that they can be optionally overridden
by platform ports.

Also, the enable_mmu_elX() functions have been moved to
lib/aarch64/xlat_tables.c for optional re-use by platform ports.
These functions are tightly coupled with the translation table
initialization code.

Fixes ARM-software/tf-issues#152

Change-Id: I0a2251ce76acfa3c27541f832a9efaa49135cc1c

Move BL porting functions into platform.h ...

Some platform porting functions were in BL specific header files.
These have been moved to platform.h so that all porting functions
are in the same place. The functions are now grouped by BL.
Obsolete BL headers files have been removed.

Also, the weak declaration of the init_bl2_mem_layout() function
has been moved out the header file and into the source file
(bl_common.c) using the more succinct #pragma syntax. This
mitigates the risk of 2 weak definitions being created and the
wrong one being picked up by the compiler.

Change-Id: Ib19934939fd755f3e5a5a5bceec88da684308a83

Split platform.h into separate headers ...

Previously, platform.h contained many declarations and definitions
used for different purposes. This file has been split so that:

* Platform definitions used by common code that must be defined
  by the platform are now in platform_def.h. The exact include
  path is exported through $PLAT_INCLUDES in the platform makefile.

* Platform definitions specific to the FVP platform are now in
  /plat/fvp/fvp_def.h.

* Platform API declarations specific to the FVP platform are now
  in /plat/fvp/fvp_private.h.

* The remaining platform API declarations that must be ported by
  each platform are still in platform.h but this file has been
  moved to /include/plat/common since this can be shared by all
  platforms.

Change-Id: Ieb3bb22fbab3ee8027413c6b39a783534aee474a