Comment 3 for bug 1783362

Following https://wiki.qemu.org/Contribute/SubmitAPatch#Make_code_motion_patches_easy_to_review:

@@ -1,5 +1,5 @@
---
--- a/linux-user/mmap.c
- if (len == 0)
- goto the_end;
--
+++ b/linux-user/mmap.c
+ if (len == 0) {
+ errno = EINVAL;
+ goto fail;
+ }