Fix typos in documentation

In the porting guide, there are blue boxes that describe the argument
types and the return type of each function.  A small typo caused some of
these boxes not being properly rendered.

In the user guide, small typos were fixed that caused random text being
unintentionally rendered as bold.  Also, a slight rewording was done in
the section describing the DYN_DISABLE_AUTH flag.

Change-Id: I57303ca609436a82162fa9b42c06b0d5a63da6df
Signed-off-by: John Tsichritzis <john.tsichritzis@arm.com>
diff --git a/docs/porting-guide.rst b/docs/porting-guide.rst
index 03930cf..a737cf4 100644
--- a/docs/porting-guide.rst
+++ b/docs/porting-guide.rst
@@ -1661,6 +1661,7 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
+
     Argument : void
     Return   : void
 
@@ -1674,6 +1675,7 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
+
     Argument : void
     Return   : int
 
@@ -1704,6 +1706,7 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
+
 	Argument : u_register_t, u_register_t, u_register_t, u_register_t
 	Return   : void
 
@@ -1726,6 +1729,7 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
+
 	Argument : void
 	Return   : void
 
@@ -1741,6 +1745,7 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
+
 	Argument : void
 	Return   : void