ARM: 9129/1: mm: Kill task_struct argument for __do_page_fault()

The __do_page_fault() won't use task_struct argument, kill it
and also use current->mm directly in do_page_fault().

No functional change.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>