Validate power_state and entrypoint when executing PSCI calls ...

This patch allows the platform to validate the power_state and
entrypoint information from the normal world early on in PSCI
calls so that we can return the error safely. New optional
pm_ops hooks `validate_power_state` and `validate_ns_entrypoint`
are introduced to do this.

As a result of these changes, all the other pm_ops handlers except
the PSCI_ON handler are expected to be successful. Also, the PSCI
implementation will now assert if a PSCI API is invoked without the
corresponding pm_ops handler being registered by the platform.

NOTE : PLATFORM PORTS WILL BREAK ON MERGE OF THIS COMMIT. The
pm hooks have 2 additional optional callbacks and the return type
of the other hooks have changed.

Fixes ARM-Software/tf-issues#229

Change-Id: I036bc0cff2349187c7b8b687b9ee0620aa7e24dc

Remove `ns_entrypoint` and `mpidr` from parameters in pm_ops ...

This patch removes the non-secure entry point information being passed
to the platform pm_ops which is not needed. Also, it removes the `mpidr`
parameter for  platform pm hooks which are meant to do power management
operations only on the current cpu.

NOTE: PLATFORM PORTS MUST BE UPDATED AFTER MERGING THIS COMMIT.

Change-Id: If632376a990b7f3b355f910e78771884bf6b12e7

Merge pull request #219 from jcastillo-arm/jc/tf-issues/253 ...

Improvements to ARM GIC driver
Juno: Use the generic ARM GIC driver

Juno: Use the generic ARM GIC driver ...

This patch replaces the usage of the GIC private driver in Juno with
the generic ARM GIC driver. The private driver is no longer necessary
and has been removed from the Juno port.

Fixes ARM-software/tf-issues#253

Change-Id: I6aaabc252e5e6fb5fcf44ab6d0febd9b38791056

Juno: Support entry into a standby state ...

This patch adds support on the Juno platform for entering a wfi in
response to a PSCI CPU_SUSPEND call where the state type is a
standby state.

Change-Id: I0a102dee1f8d2ad936c63ad1d1d3ad001a4a4768

Juno: Implement PSCI SYSTEM_OFF and SYSTEM_RESET APIs ...

This patch adds the Juno platform specific handlers for PSCI
SYSTEM_OFF and SYSTEM_RESET operations.

Change-Id: Ie389adead533ec2314af44d721b4d0f306147c7d

Juno: Implement PSCI CPU_OFF and CPU_SUSPEND APIs ...

This patch adds support for PSCI CPU_OFF and CPU_SUSPEND APIs to the Juno port
of the ARM Trusted Firmware. The maximum affinity level that can be suspended is
the cluster level (affinity level 1). Support for suspending the system level is
not present.

Change-Id: Ie2c9da0acd7d1b0d5ac64940cdf40347153e52c8

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