doc: Set correct syntax highlighting style

Several code blocks do not specify a language for syntax
highlighting. This results in Sphinx using a default highlighter
which is Python.

This patch adds the correct language to each code block that doesn't
already specify it.

Change-Id: Icce1949aabfdc11a334a42d49edf55fa673cddc3
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/perf/psci-performance-juno.rst b/docs/perf/psci-performance-juno.rst
index caed8bf..b6fd8c8 100644
--- a/docs/perf/psci-performance-juno.rst
+++ b/docs/perf/psci-performance-juno.rst
@@ -28,7 +28,7 @@
 We used the upstream `TF master as of 31/01/2017`_, building the platform using
 the ``ENABLE_RUNTIME_INSTRUMENTATION`` option:
 
-::
+.. code:: shell
 
     make PLAT=juno ENABLE_RUNTIME_INSTRUMENTATION=1 \
         SCP_BL2=<path/to/scp-fw.bin>                \