requester: Make pldm_open() return existing fd

Considering how this is used, it makes more sense to return the fd of
the open transport rather than error out.

Fixes: c1b66f420912 ("requester: Add new APIs to support multiple transports")
Change-Id: Ibff526a013d0f4000217d8b0b1004ff51814d820
Signed-off-by: Rashmica Gupta <rashmica@linux.ibm.com>
diff --git a/src/requester/pldm.c b/src/requester/pldm.c
index 973f194..21e402e 100644
--- a/src/requester/pldm.c
+++ b/src/requester/pldm.c
@@ -31,7 +31,8 @@
 	int rc;
 
 	if (open_transport) {
-		return -1;
+		fd = pldm_transport_mctp_demux_get_socket_fd(open_transport);
+		return fd;
 	}
 
 	struct pldm_transport_mctp_demux *demux = NULL;