Don't warn if mapping p2 dependencies is not enabled

If mapping p2 dependencies is not enabled there should be no warning but
just an info message about the number.

(cherry picked from commit ce3b3d1)

tycho-packaging-plugin/src/main/java/org/eclipse/tycho/packaging/UpdateConsumerPomMojo.java

@@ -259,14 +259,16 @@ public void execute() throws MojoExecutionException, MojoFailureException {
 		}
 		if (p2Skipped.isEmpty()) {
 			log.info("All system scoped dependencies were mapped to maven artifacts");
-		} else {
+		} else if (mapP2Dependencies) {
 			log.warn(resolved + " system scoped dependencies were mapped to maven artifacts, " + p2Skipped.size()
 					+ " were skipped");
 			if (log.isDebugEnabled()) {
 				for (String skipped : p2Skipped) {
 					log.debug("Skipped: " + skipped);
 				}
 			}
+		} else {
+			log.info(p2Skipped.size() + " system scoped dependencies were not mapped to maven artifacts");
 		}
 		try {
 			modelWriter.write(output, null, projectModel);