doxygen: make sure the right C source files are included
diff --git a/Doxyfile.vty b/Doxyfile.vty
index 8536e61..91d37a6 100644
--- a/Doxyfile.vty
+++ b/Doxyfile.vty
@@ -610,7 +610,7 @@
 # directories like "/usr/src/myproject". Separate the files or directories
 # with spaces.
 
-INPUT                  = include/osmocom/vty src/vty/*.c
+INPUT                  = include/osmocom/vty src/vty
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is