ANDROID: binder: clarify deferred thread work.

Rename the function to more accurately reflect what
it does, and add a comment explaining why we use it.

Change-Id: I8d011c017dfc6e24b5b54fc462578f8e153e5926
Signed-off-by: Martijn Coenen <maco@android.com>
Git-commit: dac2e9ca
Git-repo: https://android.googlesource.com/kernel/common


Signed-off-by: Kyle Yan <kyan@codeaurora.org>