Introduce generic shutdown_free() and remove redundant internal_shutdown()

The former will be useful in cases where cleanup equals a simple call to free().

Corresponding to flashrom svn r1848.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
diff --git a/flashrom.c b/flashrom.c
index 01c1d03..9b82d4c 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -373,6 +373,12 @@
 
 static int check_block_eraser(const struct flashctx *flash, int k, int log);
 
+int shutdown_free(void *data)
+{
+	free(data);
+	return 0;
+}
+
 /* Register a function to be executed on programmer shutdown.
  * The advantage over atexit() is that you can supply a void pointer which will
  * be used as parameter to the registered function upon programmer shutdown.