Update Arm TF references to TF-A ...

Update Arm Trusted Firmware references in the upstream documents to
Trusted Firmware-A (TF-A). This is for consistency with and
disambiguation from Trusted Firmware-M (TF-M).

Also update other Arm trademarks, e.g. ARM->Arm, ARMv8->Armv8-A.

Change-Id: I8bb0e18af29c6744eeea2dc6c08f2c10b20ede22
Signed-off-by: Dan Handley <dan.handley@arm.com>
Signed-off-by: David Cunado <david.cunado@arm.com>

rpi3: Add documentation of Raspberry Pi 3 port ...

Added design documentation and usage guide for the AArch64 port of the
Arm Trusted Firmware to the Raspberry Pi 3.

Change-Id: I1be60fbbd54c797b48a1bcebfb944d332616a0de
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>