Use the 'tiny' GCC memory model

[athoelke]

The Trusted Firmware executables are currently compiled with the default 'small' GCC memory model. This model requires that all internal references from code to code and/or data are within +/-4GB.

GCC provides a more compact memory model - 'tiny' - if the code and data all lie within +/-1MB that generates more compact code (BL3-1 for FVP with TSP is about 250 bytes smaller).

This memory model is appropriate for BL2, BL3-1 and BL3-2 which are all small contiguous executables, but not for BL1 which is split with code in ROM and data in RAM (at least on FVP).

It should be possible to select an appropriate memory model for each image, rather than use the same model for all of them, and benefit from the smaller faster code that this generates.

[sandrine-bailleux-arm]

Internal ref: http://jira.arm.com/browse/GENFW-1326