This patch adds Firmware Update support for ARM platforms.

New files arm_bl1_fwu.c and juno_bl1_setup.c were added to provide
platform specific Firmware update code.

BL1 now includes mmap entry for `ARM_MAP_NS_DRAM1` to map DRAM for
authenticating NS_BL2U image(For both FVP and JUNO platform).

Change-Id: Ie116cd83f5dc00aa53d904c2f1beb23d58926555