fix(fvp): work around DRTM_SUPPORT BL31 progbits exceeded

fix(fvp): work around DRTM_SUPPORT BL31 progbits exceeded

Just like the tspd, DRTM support pulls in a lot of code which can't fit
into SRAM with everything else the fvp is including. Luckily, testing
this feature is only done on v8.0 models, meaning all feature related
code can be excluded for this run, saving space. The benefit of doing it
this way is that the test can continue running unaltered in the interim.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: Iced2089837622fea49c10ae403c653dd1f331ca3