CODINGSTYLE.md: add the rule for '*' and '&'

C++ coding convention is to bind '*' and '&' to the type,
not to the variable.

Signed-off-by: Zhi Yong Wu <zwu.kernel@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

CODINGSTYLE.md

@@ -49,6 +49,12 @@ template and its paramters.
    std::vector<object*>
 ```
 
+2.4 Bind '*' or '&' to the type, not the variable
+...
+   int* a;
+   int& b;
+...
+
 ## 3. Braces
 3.1 Always use curly braces for if statement, even if it is a one line if.