.travis.yml: omit linux-ppc64le target.

Build jobs keep timing out initializing...
Reviewed-by: NKurt Roeckx <kurt@roeckx.be>

.travis.yml

@@ -31,10 +31,10 @@ env:
 
 matrix:
     include:
-        - os: linux-ppc64le
-          sudo: false
-          compiler: clang
-          env: CONFIG_OPTS="--strict-warnings -D__NO_STRING_INLINES"
+        #- os: linux-ppc64le
+        #  sudo: false
+        #  compiler: clang
+        #  env: CONFIG_OPTS="--strict-warnings -D__NO_STRING_INLINES"
         - os: linux
           addons:
               apt: