Fix build option 'ARM_TSP_RAM_LOCATION' in user guide
Juan Castillo authored
The 'ARM_TSP_RAM_LOCATION_ID' option specified in the user guide
corresponds to the internal definition not visible to the final
user. The proper build option is 'ARM_TSP_RAM_LOCATION'. This
patch fixes it.

Fixes ARM-software/tf-issues#308

Change-Id: Ica8cb72c0c5e8b3503f60b5357d16698e869b1bd
e5da24f7