Add lsk-vexpress key.

Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>
diff --git a/build_images.py b/build_images.py
index 9b71278..06d13c3 100755
--- a/build_images.py
+++ b/build_images.py
@@ -57,6 +57,7 @@
     'highbank': HwPack('highbank'),
     'igep': HwPack('igep'),
     'leb-origen': HwPack('origen'),
+    'lsk-vexpress': HwPack('vexpress'),
     'lt-mx5': HwPack('mx53loco'),
     'lt-mx6': HwPack('mx6qsabrelite'),
     'lt-origen': HwPack('origen'),