doc: Misc syntax and spelling fixes

Tidying up a few Sphinx warnings that had built-up over time.
None of these are critical but it cleans up the Sphinx output.

At the same time, fixing some spelling errors that were detected.

Change-Id: I38209e235481eed287f8008c6de9dedd6b12ab2e
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 4cc4302..c127c1c 100644
--- a/docs/perf/psci-performance-juno.rst
+++ b/docs/perf/psci-performance-juno.rst
@@ -168,7 +168,7 @@
 | 5     | 21                  | 17                 | 6                        |
 +-------+---------------------+--------------------+--------------------------+
 
-The ``CLUSH_OVERHEAD`` times for lead CPU 4 and all CPUs in the non-lead cluster
+The ``CFLUSH_OVERHEAD`` times for lead CPU 4 and all CPUs in the non-lead cluster
 are large because all other CPUs in the cluster are powered down during the
 test. The ``CPU_SUSPEND`` call powers down to the cluster level, requiring a
 flush of both L1 and L2 caches.