tfa-next: test STF on CI on fvp

Test secure world support as the default option.

The current build system is limited on what it can actually
build, so change the build configuration to build STF with
the current setup. Please see:

https://github.com/RustedFirmware-A/rusted-firmware-a/issues/59

for more information.

Change-Id: If812dcbe2e33883b43a46e6b1b2c760ed4be841d
Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
7 files changed