[roll] Roll fuchsia [musl] Update socket.h

git show musl/master:include/sys/socket.h > zircon/third_party/ulib/musl/include/sys/socket.h

Importantly picks up a UB fix in CMSG_NXTHDR, see
https://git.musl-libc.org/cgit/musl/commit?id=81fb75a1d75c20d97292cbbe.

Manually fixed comparison of integers with different signs:
```
diff --git a/zircon/third_party/ulib/musl/include/sys/socket.h b/zircon/third_party/ulib/musl/include/sys/socket.h
index be2050d4ae6..a93211a2c2c 100644
--- a/zircon/third_party/ulib/musl/include/sys/socket.h
+++ b/zircon/third_party/ulib/musl/include/sys/socket.h
@@ -352,10 +351,11 @@ struct linger {
 #define __MHDR_END(mhdr) ((unsigned char*)(mhdr)->msg_control + (mhdr)->msg_controllen)

 #define CMSG_DATA(cmsg) ((unsigned char*)(((struct cmsghdr*)(cmsg)) + 1))
-#define CMSG_NXTHDR(mhdr, cmsg)                                                                   \
-  ((cmsg)->cmsg_len < sizeof(struct cmsghdr) ||                                                   \
-           __CMSG_LEN(cmsg) + sizeof(struct cmsghdr) >= __MHDR_END(mhdr) - (unsigned char*)(cmsg) \
-       ? 0                                                                                        \
+#define CMSG_NXTHDR(mhdr, cmsg)                                    \
+  ((cmsg)->cmsg_len < sizeof(struct cmsghdr) ||                    \
+           (ssize_t)(__CMSG_LEN(cmsg) + sizeof(struct cmsghdr)) >= \
+               __MHDR_END(mhdr) - (unsigned char*)(cmsg)           \
+       ? 0                                                         \
        : (struct cmsghdr*)__CMSG_NEXT(cmsg))
 #define CMSG_FIRSTHDR(mhdr)                                                                        \
   ((size_t)(mhdr)->msg_controllen >= sizeof(struct cmsghdr) ? (struct cmsghdr*)(mhdr)->msg_control \
```

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/606023
Original-Revision: 049ac5352f60b670f3bcac046731fc85eedbd290
GitOrigin-RevId: 1d6e6580ec40ace5d67702fa42eab4499d738b59
Change-Id: Iac16dd7aea5c382625a49632e411a0b4b201ec4b