Remove platform dependency in CCI-400 driver

* Create cci_init() function in CCI-400 driver to allow platform
  to provide arguments needed by the driver (i.e. base address
  and cluster indices for the ACE slave interfaces).

* Rename cci_(en|dis)able_coherency to
  cci_(en|dis)able_cluster_coherency to make it clear that
  the driver only enables/disables the coherency of CPU
  clusters and not other devices connected to the CCI-400.

* Update FVP port to use new cci_init() function and remove
  unnecessary CCI defintions from platform_def.h. Also rename
  fvp_cci_setup() to fvp_cci_enable() to more clearly
  differentiate between CCI initialization and enabling.

THIS CHANGE REQUIRES PLATFORM PORTS THAT USE THE CCI-400 DRIVER
TO BE UPDATED

Fixes ARM-software/tf-issues#168

Change-Id: I1946a51409b91217b92285b6375082619f607fec
Remove redundant io_init() function

The intent of io_init() was to allow platform ports to provide
a data object (io_plat_data_t) to the IO storage framework to
allocate into. The abstraction was incomplete because io_plat_data_t
uses a platform defined constant and the IO storage framework
internally allocates other arrays using platform defined constants.

This change simplifies the implementation by instantiating the
supporting objects in the IO storage framework itself. There is now
no need for the platform to call io_init().

The FVP port has been updated accordingly.

THIS CHANGE REQUIRES ALL PLATFORM PORTS THAT USE THE IO STORAGE
FRAMEWORK TO BE UDPATED.

Change-Id: Ib48ac334de9e538064734334c773f8b43df3a7dc
Move IO storage source to drivers directory

Move the remaining IO storage source file (io_storage.c) from the
lib to the drivers directory. This requires that platform ports
explicitly add this file to the list of source files.

Also move the IO header files to a new sub-directory, include/io.

Change-Id: I862b1252a796b3bcac0d93e50b11e7fb2ded93d6
Simplify interface to TZC-400 driver

The TZC-400 driver previously allowed the possibility of multiple
controller instances to be present in the same executable. This
was unnecessary since there will only ever be one instance.

This change simplifies the tzc_init() function to only take the
base address argument needed by implementation, conforming to the
driver initialization model of other drivers. It also hides some
of the implementation details that were previously exposed by the
API.

The FVP port has been updated accordingly.

THIS CHANGE REQUIRES ALL PLATFORM PORTS THAT USE THE TZC-400
DRIVER TO BE UPDATED

Fixes ARM-software/tf-issues#181

Change-Id: I7b721edf947064989958d8f457d6462d92e742c8
Merge pull request #185 from danh-arm/dh/refactor-drivers

Refactor platform porting interface to drivers