UPSTREAM: binder: remove kernel vm_area for buffer space

Remove the kernel's vm_area and the code that maps
buffer pages into it.

(cherry pick from commit 880211667b203dd32724f3be224c44c0400aa0a6)
Bug: 67668716
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Change-Id: I2595bb8416c2bbfcf97ad3d7380ae94e29c209fb