media: cec-pin-error-inj.rst: document CEC Pin Error Injection

The CEC Pin framework adds support for Error Injection.

Document all the error injections commands and how to use it.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/cec/cec-api.rst

@@ -23,6 +23,7 @@ This part describes the CEC: Consumer Electronics Control
 
     cec-intro
     cec-funcs
+    cec-pin-error-inj
     cec-header