polish language update by Maciej Adamczak

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17899 a1c6a512-1295-4272-9138-f99709370657
diff --git a/docs/CREDITS b/docs/CREDITS
index 131aeba..321b249 100644
--- a/docs/CREDITS
+++ b/docs/CREDITS
@@ -395,6 +395,7 @@
 Mohamed Tarek
 Mike Burke
 Michael Chicoine
+Maciej Adamczak
 
 The libmad team
 The wavpack team