Travis-CI: Add job for running test.py on qemu_arm64

The corresponding changes in the uboot-test-hooks repo are:

https://github.com/swarren/uboot-test-hooks/pull/15

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Reviewed-by: Tom Rini <trini@konsulko.com>

.travis.yml

@@ -339,6 +339,11 @@ matrix:
           QEMU_TARGET="arm-softmmu"
           BUILDMAN="^qemu_arm$"
     - env:
+        - TEST_PY_BD="qemu_arm64"
+          TEST_PY_TEST_SPEC="not sleep"
+          QEMU_TARGET="aarch64-softmmu"
+          BUILDMAN="^qemu_arm64$"
+    - env:
         - TEST_PY_BD="qemu_mips"
           TEST_PY_TEST_SPEC="not sleep"
           QEMU_TARGET="mips-softmmu"