Fix return types of sendMessageOnSocket/receiveMessageFromSocket

recvmsg() and sendmsg() return ssize_t but the wrapper functions
returned int. Fix the return type.

Bug: 250685929
Test: atest rpcBinderTest
Change-Id: Ia3f7f58e286f24a8711aed97d9bc2b3cf6b78f0d
diff --git a/libs/binder/OS.cpp b/libs/binder/OS.cpp
index 77e401f..ce60e33 100644
--- a/libs/binder/OS.cpp
+++ b/libs/binder/OS.cpp
@@ -67,7 +67,7 @@
     return RpcTransportCtxFactoryRaw::make();
 }
 
-int sendMessageOnSocket(
+ssize_t sendMessageOnSocket(
         const RpcTransportFd& socket, iovec* iovs, int niovs,
         const std::vector<std::variant<base::unique_fd, base::borrowed_fd>>* ancillaryFds) {
     if (ancillaryFds != nullptr && !ancillaryFds->empty()) {
@@ -112,7 +112,7 @@
     return TEMP_FAILURE_RETRY(sendmsg(socket.fd.get(), &msg, MSG_NOSIGNAL));
 }
 
-int receiveMessageFromSocket(
+ssize_t receiveMessageFromSocket(
         const RpcTransportFd& socket, iovec* iovs, int niovs,
         std::vector<std::variant<base::unique_fd, base::borrowed_fd>>* ancillaryFds) {
     if (ancillaryFds != nullptr) {