Disable compilation of extra images from qssi builds

QSSI build step should only build images related to system
but not the extra images as these will be built during the
non-system build step.

Files Affected:
- qssi.mk

Test:
- Local compilation

Change-Id: If8f0964beff690df5b82656eb11fc5a5f94cf8c1
2 files changed