FROMLIST: binder: fix an ret value override

(from https://patchwork.kernel.org/patch/9939409/

)

commit 372e3147df70 ("binder: guarantee txn complete / errors delivered
in-order") incorrectly defined a local ret value.  This ret value will
be invalid when out of the if block

Change-Id: If7bd963ac7e67d135aa949133263aac27bf15d1a
Signed-off-by: Xu YiPing <xuyiping@hislicon.com>
Signed-off-by: Todd Kjos <tkjos@google.com>