travis: Build aspeed board with qemu HEAD

In order to boot u-boot in the aspeed machine we need to run at least
qemu 3059c2f5a813 (v4.0.0-1592-g3059c2f5a813), which is not in a
released tag.

This should be changed to v4.1.0 when it is released.

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/.travis.yml b/.travis.yml
index 6abfa5d..d586644 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -392,7 +392,7 @@
         - TEST_PY_BD="evb-ast2500"
           TEST_PY_ID="--id qemu"
           QEMU_TARGET="arm-softmmu"
-          QEMU_VERSION="v4.0.0"
+          QEMU_VERSION="506179e42112be77bfd071f050b15762d3b2cd43"
           BUILDMAN="^evb-ast2500$"
     - name: "test/py vexpress_ca15_tc2"
       env: