ci: add minimal check on testpmd

Try to start testpmd with two vdevs without hugepages.
This is a really basic check, but better than nothing.

Signed-off-by: David Marchand <david.marchand@redhat.com>

.ci/linux-build.sh

@@ -32,6 +32,10 @@ OPTS="$OPTS --default-library=$DEF_LIB"
 meson build --werror -Dexamples=all $OPTS
 ninja -C build
 
+if [ "$AARCH64" != "1" ]; then
+    devtools/test-null.sh
+fi
+
 if [ "$RUN_TESTS" = "1" ]; then
     sudo meson test -C build --suite fast-tests -t 3
 fi