travis-ci: OrangePi PC2 only links with gcc-5.x or later

We disable this specific board as it does not link with the gcc-4.9.x
that we use today in travis-ci.

Signed-off-by: Tom Rini <trini@konsulko.com>

.travis.yml

@@ -152,7 +152,7 @@ matrix:
     - env:
         - BUILDMAN="sun7i"
     - env:
-        - BUILDMAN="sun8i"
+        - BUILDMAN="sun8i -x orangepi_pc2"
     - env:
         - BUILDMAN="sun9i"
     - env: