Fix #include path in ARM platform BL1 setup code
Fix #include path in ARM platform BL1 setup code

This patch fixes the relative path to the 'bl1_private.h' header file
included from 'arm_bl1_setup.c'. Note that, although the path was
incorrect, it wasn't causing a compilation error because the header
file still got included through an alternative include search path.

Change-Id: I28e4f3dbe50e3550ca6cad186502c88a9fb5e260

sandrine-bailleux/arm-trusted-firmware,sandrine-bailleux/arm-trusted-firmware,achingupta/arm-trusted-firmware,lsigithub/arm-trusted-firmware_public,lsigithub/arm-trusted-firmware_public,davwan01/arm-trusted-firmware,davwan01/arm-trusted-firmware,jcastillo-arm/arm-trusted-firmware,achingupta/arm-trusted-firmware,jcastillo-arm/arm-trusted-firmware,sbranden/arm-trusted-firmware,sandrine-bailleux-arm/arm-trusted-firmware,sbranden/arm-trusted-firmware,sandrine-bailleux-arm/arm-trusted-firmware