Revert "Use std::function instead of base::function_ref"

Revert submission 2780893

Reason for revert: breaking boot tests

Bug: 308214260

Reverted changes: /q/submissionid:2780893

Change-Id: Ibbd9bf2c9eb1389c9b8217cc75a98a3ec13b77d8
diff --git a/libs/binder/RpcTransportUtils.h b/libs/binder/RpcTransportUtils.h
index a0e502e..32f0db8 100644
--- a/libs/binder/RpcTransportUtils.h
+++ b/libs/binder/RpcTransportUtils.h
@@ -27,7 +27,7 @@
 status_t interruptableReadOrWrite(
         const android::RpcTransportFd& socket, FdTrigger* fdTrigger, iovec* iovs, int niovs,
         SendOrReceive sendOrReceiveFun, const char* funName, int16_t event,
-        const std::optional<binder::impl::SmallFunction<status_t()>>& altPoll) {
+        const std::optional<android::base::function_ref<status_t()>>& altPoll) {
     MAYBE_WAIT_IN_FLAKE_MODE;
 
     if (niovs < 0) {