staging: android: binder: Move some of the logic into subfunction

This patch moves some of the logic for binder_thread_write() into
subfunctions. This way we can share more code with the binder compat
layer.

Change-Id: Ibe2eb9c0deccc229d2b075f08271531db1aa00ed
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>
Git-commit: 6263502420f43e6b4b154bc7c1e55cd37f9628ed
Git-repo: git://linux-arm.org/linux-2.6-armdroid.git


Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>