Added a new platform porting function plat_panic_handler, to allow
platforms to handle unexpected error situations. It must be
implemented in assembly as it may be called before the C environment
is initialized. A default implementation is provided, which simply
spins.

Corrected all dead loops in generic code to call this function
instead. This includes the dead loop that occurs at the end of the
call to panic().

All unnecesary wfis from bl32/tsp/aarch64/tsp_exceptions.S have
been removed.

Change-Id: I67cb85f6112fa8e77bd62f5718efcef4173d8134

The default reset values for the L2 Data & Tag RAM latencies on the
Cortex-A72 on Juno R2 are not suitable. This patch modifies
the Juno platform reset handler to configure the right settings
on Juno R2.

Change-Id: I20953de7ba0619324a389e0b7bbf951b64057db8

This patch splits the Juno reset handler in 4 distinct pieces:

 - Detection of the board revision;
 - Juno R0 specific handler;
 - Juno R1 specific handler;
 - Juno R2 specific handler.

Depending on the board revision, the appropriate handler is called.
This makes the code easier to understand and maintain.

This patch is mainly cosmetic. The only functional change introduced
is that the Juno platform reset handler will now spin infinitely if
the board revision is not recognised. Previously, it would have
assumed that it was running on Juno R1 in this case.

Change-Id: I54ed77c4665085ead9d1573316c9c884d7d3ffa0

Currently all ARM CSS platforms which include css_helpers.S use the same
strong definition of `plat_arm_calc_core_pos`. This patch allows these CSS
platforms to define their own strong definition of this function.

* Replace the strong definition of `plat_arm_calc_core_pos` in
  css_helpers.S with a utility function `css_calc_core_pos_swap_cluster`
  does the same thing (swaps cluster IDs). ARM CSS platforms may choose
  to use this function or not.

* Add a Juno strong definition of `plat_arm_calc_core_pos`, which uses
  `css_calc_core_pos_swap_cluster`.

Change-Id: Ib5385ed10e44adf6cd1398a93c25973eb3506d9d

This patch removes the FIRST_RESET_HANDLER_CALL build flag and its
use in ARM development platforms. If a different reset handling
behavior is required between the first and subsequent invocations
of the reset handling code, this should be detected at runtime.

On Juno, the platform reset handler is now always compiled in.
This means it is now executed twice on the cold boot path, first in
BL1 then in BL3-1, and it has the same behavior in both cases. It is
also executed twice on the warm boot path, first in BL1 then in the
PSCI entrypoint code.

Also update the documentation to reflect this change.

NOTE: THIS PATCH MAY FORCE PLATFORM PORTS THAT USE THE
FIRST_RESET_HANDLER_CALL BUILD OPTION TO FIX THEIR RESET HANDLER.

Change-Id: Ie5c17dbbd0932f5fa3b446efc6e590798a5beae2

Move the Juno port from plat/juno to plat/arm/board/juno. Also rename
some of the files so they are consistently prefixed with juno_.
Update the platform makefiles accordingly.

Change-Id: I0af6cb52a5fee7ef209107a1188b76a3c33a2a9f