Revert "slirp: Fix migration break on incorrect vmstate retcode"

This reverts commit cb2755b3134650f380c3fbb697f507a6b53bad26.

src/vmstate.c

diff --git a/src/vmstate.c b/src/vmstate.c
index 5194680..535cc68 100644
--- a/src/vmstate.c
+++ b/src/vmstate.c
@@ -240,13 +240,13 @@
 static int get_buffer(SlirpIStream *f, void *pv, size_t size,
                       const VMStateField *field)
 {
-    return !slirp_istream_read(f, pv, size);
+    return slirp_istream_read(f, pv, size);
 }
 
 static int put_buffer(SlirpOStream *f, void *pv, size_t size,
                       const VMStateField *field)
 {
-    return !slirp_ostream_write(f, pv, size);
+    return slirp_ostream_write(f, pv, size);
 }
 
 const VMStateInfo slirp_vmstate_info_buffer = {