pkg: updated patching information

pkg/PORTING.md

@@ -3,12 +3,12 @@ use with RIOT (to build an external module). If you'd like to add a package to
 RIOT you need to add a directory with the name of your package to this directory.
 Your directory should contain at least two files:
 
- * **patch.txt**- Your patch of the upstream application of the package to make
- it build with RIOT.
- * **Makefile**- A Makefile describing how to get the upstream application, apply
- the patch and how to build the package as a RIOT module.
- A rough template for several methods of acquiring a package
- is provided in Makefile.git, Makefile.http, and Makefile.svn
+ * **One or more patch files** - Your patches of the upstream application of
+   the package to make it build with RIOT.
+ * **Makefile**- A Makefile describing how to get the upstream application,
+   apply the patch and how to build the package as a RIOT module.
+   A rough template for several methods of acquiring a package is provided in
+   Makefile.git, Makefile.http, and Makefile.svn
 
 ### Creating a patch with git