Optimize Cortex-A57 cluster power down sequence on Juno ...

This patch optimizes the Cortex-A57 cluster power down sequence by not
flushing the Level1 data cache. The L1 data cache and the L2 unified
cache are inclusive. A flush of the L2 by set/way flushes any dirty
lines from the L1 as well. This is a known safe deviation from the
Cortex-A57 TRM defined power down sequence. This optimization can be
enabled by the platform through the 'SKIP_A57_L1_FLUSH_PWR_DWN' build
flag. Each Cortex-A57 based platform must make its own decision on
whether to use the optimization.

This patch also renames the cpu-errata-workarounds.md to
cpu-specific-build-macros.md as this facilitates documentation
of both CPU Specific errata and CPU Specific Optimization
build macros.

Change-Id: I299b9fe79e9a7e08e8a0dffb7d345f9a00a71480

Juno: Reserve some DDR-DRAM for secure use ...

This patch configures the TrustZone Controller in Juno to split
the 2GB DDR-DRAM memory at 0x80000000 into Secure and Non-Secure
regions:

- Secure DDR-DRAM: top 16 MB, except for the last 2 MB which are
  used by the SCP for DDR retraining
- Non-Secure DDR-DRAM: remaining DRAM starting at base address

Build option PLAT_TSP_LOCATION selects the location of the secure
payload (BL3-2):

- 'tsram' : Trusted SRAM (default option)
- 'dram'  : Secure region in the DDR-DRAM (set by the TrustZone
            controller)

The MMU memory map has been updated to give BL2 permission to load
BL3-2 into the DDR-DRAM secure region.

Fixes ARM-software/tf-issues#233

Change-Id: I6843fc32ef90aadd3ea6ac4c7f314f8ecbd5d07b

Juno: Use TZC-400 driver calls ...

This patch replaces direct accesses to the TZC-400 registers by the
appropiate calls to the generic driver available in the Trusted
Firmware in order to initialize the TrustZone Controller.

Functions related to the initialization of the secure memory,
like the TZC-400 configuration, have been moved to a new file
'plat_security.c'. This reorganization makes easier to set up
the secure memory from any BL stage.

TZC-400 initialization has been moved from BL1 to BL2 because BL1
does not access the non-secure memory. It is BL2's responsibility
to enable and configure the TZC-400 before loading the next BL
images.

In Juno, BL3-0 initializes some of the platform peripherals, like
the DDR controller. Thus, BL3-0 must be loaded before configuring
the TrustZone Controller. As a consequence, the IO layer
initialization has been moved to early platform initialization.

Fixes ARM-software/tf-issues#234

Change-Id: I83dde778f937ac8d2996f7377e871a2e77d9490e

Juno: Implement initial platform port ...

This patch adds the initial port of the ARM Trusted Firmware on the Juno
development platform. This port does not support a BL3-2 image or any PSCI APIs
apart from PSCI_VERSION and PSCI_CPU_ON. It enables workarounds for selected
Cortex-A57 (#806969 & #813420) errata and implements the workaround for a Juno
platform errata (Defect id 831273).

Change-Id: Ib3d92df3af53820cfbb2977582ed0d7abf6ef893