android: binder: Change return type to vm_fault_t

Use new return type vm_fault_t for fault handler in
struct vm_operations_struct. For now, this is just
documenting that the function returns a VM_FAULT
value rather than an errno.  Once all instances are
converted, vm_fault_t will become a distinct type.

Reference id -> 1c8f4220 ("mm: change return type
to vm_fault_t")

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>