libbinder: remove unused IPCThreadState::process

This function isn't used, and ProcessState is a global object.

Future consideration:
- would it be worth the saved memory in thread local storage to drop
  IPCThreadState::mProcess and reference the global?

Bug: N/A
Test: N/A
Change-Id: I984f57827d3ade423b24132dd5b5f18028dc2a1d
diff --git a/libs/binder/IPCThreadState.cpp b/libs/binder/IPCThreadState.cpp
index 55d3d70..13f0a4c 100644
--- a/libs/binder/IPCThreadState.cpp
+++ b/libs/binder/IPCThreadState.cpp
@@ -352,11 +352,6 @@
     return gDisableBackgroundScheduling.load(std::memory_order_relaxed);
 }
 
-sp<ProcessState> IPCThreadState::process()
-{
-    return mProcess;
-}
-
 status_t IPCThreadState::clearLastError()
 {
     const status_t err = mLastError;
diff --git a/libs/binder/include/binder/IPCThreadState.h b/libs/binder/include/binder/IPCThreadState.h
index 82bebc9..bf02099 100644
--- a/libs/binder/include/binder/IPCThreadState.h
+++ b/libs/binder/include/binder/IPCThreadState.h
@@ -54,8 +54,6 @@
     static  status_t            getProcessFreezeInfo(pid_t pid, uint32_t *sync_received,
                                                     uint32_t *async_received);
 
-            sp<ProcessState>    process();
-
             status_t            clearLastError();
 
             /**