ci: travis: run only code check and QEMU regression
ci: travis: run only code check and QEMU regression

This is the first of two commits to split the CI work in two: Travis
should run checkpatch and the QEMU regression (xtest), while Shippable
should run the platform builds. By doing so, we better utilize the
resources and hopefully minimize build timeouts.

Signed-off-by: Jerome Forissier <ced78d268b4c9a0a20a59a9feeebd2ad90da03d3@linaro.org>
Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>

pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os