Add a uptr_t type that can hold a pointer to either a user or kernel
memory region, and simply helpers to copy to and from it.
Change-Id: I022ad4e2dbc41c146548eef16c53d523ab021cfb
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>