char: headers clean-up

Those could probably be squashed with earlier patches, however I
couldn't easily identify them, test them or check if there are still
necessary on various platforms.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/hmp.c b/hmp.c
index 8522efe..2bc4f06 100644
--- a/hmp.c
+++ b/hmp.c
@@ -19,6 +19,7 @@
 #include "net/eth.h"
 #include "sysemu/char.h"
 #include "sysemu/block-backend.h"
+#include "qemu/config-file.h"
 #include "qemu/option.h"
 #include "qemu/timer.h"
 #include "qmp-commands.h"