Major update to the Juno platform port to use the common platform code
in (include/)plat/arm/* and (include/)plat/common/*. This mainly
consists of removing duplicated code but also introduces some small
behavioural changes where there was unnecessary variation between the
FVP and Juno ports. See earlier commit titled `Add common ARM and CSS
platform code` for details.

Also move the ARM SoC specific security setup (i.e. NIC-400 and PCIe
initialization) from BL1 to `plat_arm_security_setup()` in BL2,
where the other security setup is done.

Change-Id: Ic9fe01bae8ed382bfb04fc5839a4cfff332eb124