android: binder: refactor binder_transact()

Moved handling of fixup for binder objects,
handles and file descriptors into separate
functions.

Change-Id: If6849f1caee3834aa87d0ab08950bb1e21ec6e38
Signed-off-by: Martijn Coenen <maco@google.com>
Git-commit: 70301cb0
Git-repo: https://android.googlesource.com/kernel/common


[schikk@codeaurora.org  resolved merge conflicts]
Signed-off-by: Swetha Chikkaboraiah <schikk@codeaurora.org>