ANDROID: fix binder change in merge of 4.9.188

ANDROID: fix binder change in merge of 4.9.188

The 4.9.188 merge was missing the change to the
binder driver associated with the linux-4.9.y
commit 16903f1a5ba7 ("coredump: fix race condition
between mmget_not_zero()/get_task_mm() and core dumping").
It was left out because the android-4.9 binder
driver has been significantly refactored compared
to linux-4.9.y.

This patch applies the missing change from that
patch to the binder driver.

Mot-CRs-fixed: (CR)
CVE-Fixed: CVE-2019-11599
BUG: 131964235

Change-Id: I1402cf3c28f1336da9d942abeb322f71a9b8138b
Signed-off-by: Pachipulusu Bhanu Prakash <bhprakas@motorola.com>
Reviewed-on: https://gerrit.mot.com/1473937
SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver
Tested-by: Jira Key
Reviewed-by: Xiangpo Zhao <zhaoxp3@motorola.com>
Submit-Approved: Jira Key
(cherry picked from commit 99335914ba19281d60062a035e452e5527cf51a3)