ANDROID: fix ENOMEM check of binder_proc_ext

The check should be done against 'eproc' before it gets dereferenced.

Fixes: d49297739550 ("BACKPORT: binder: use euid from cred instead of using task")
Change-Id: Ief0c08212c4da8bdfdf628474de9dd30ee5a8db0
Signed-off-by: Carlos Llamas <cmllamas@google.com>