mctp-demux-daemon: Resolve uninitialised variable warning

Multiple error paths in client_process_recv() failed to set rc before returning
it from the out_close label:

    utils/mctp-demux-daemon.c: In function ‘main’:
    utils/mctp-demux-daemon.c:457:7: error: ‘rc’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
      457 |    if (rc)
          |       ^
    utils/mctp-demux-daemon.c:307:6: note: ‘rc’ was declared here
      307 |  int rc;
          |      ^~
    cc1: all warnings being treated as errors

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I4196a2b5f7b242c53921040fead102525c92a286
diff --git a/utils/mctp-demux-daemon.c b/utils/mctp-demux-daemon.c
index da69210..d223279 100644
--- a/utils/mctp-demux-daemon.c
+++ b/utils/mctp-demux-daemon.c
@@ -327,6 +327,7 @@
 	len = recv(client->sock, NULL, 0, MSG_PEEK | MSG_TRUNC);
 	if (len < 0) {
 		warn("can't receive(peek) from client");
+		rc = -1;
 		goto out_close;
 	}
 
@@ -336,6 +337,7 @@
 		tmp = realloc(ctx->buf, len);
 		if (!tmp) {
 			warn("can't allocate for incoming message");
+			rc = -1;
 			goto out_close;
 		}
 		ctx->buf = tmp;
@@ -345,6 +347,7 @@
 	rc = recv(client->sock, ctx->buf, ctx->buf_size, 0);
 	if (rc < 0) {
 		warn("can't receive from client");
+		rc = -1;
 		goto out_close;
 	}