staging: android: ion: Remove unused declaration ion_buffer_fault_user_mappings

ion_buffer_fault_user_mappings's definition has been removed and not be
used anymore, just remove its useless declaration.
Acked-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion.h

@@ -192,15 +192,6 @@ struct ion_heap {
  */
 bool ion_buffer_cached(struct ion_buffer *buffer);
 
-/**
- * ion_buffer_fault_user_mappings - fault in user mappings of this buffer
- * @buffer:		buffer
- *
- * indicates whether userspace mappings of this buffer will be faulted
- * in, this can affect how buffers are allocated from the heap.
- */
-bool ion_buffer_fault_user_mappings(struct ion_buffer *buffer);
-
 /**
  * ion_device_add_heap - adds a heap to the ion device
  * @heap:		the heap to add