Change table chaining layout

Change the page member of the scatterlist structure to be an unsigned
long, and encode more stuff in the lower bits:

- Bits 0 and 1 zero: this is a normal sg entry. Next sg entry is located
  at sg + 1.
- Bit 0 set: this is a chain entry, the next real entry is at ->page_link
  with the two low bits masked off.
- Bit 1 set: this is the final entry in the sg entry. sg_next() will return
  NULL when passed such an entry.

It's thus important that sg table users use the proper accessors to get
and set the page member.

Signed-off-by: Jens Axboe <[email protected]>

include/asm-v850/scatterlist.h

@@ -17,7 +17,7 @@
 #include <asm/types.h>
 
 struct scatterlist {
-	struct page	*page;
+	unsigned long	page_link;
 	unsigned	offset;
 	dma_addr_t	dma_address;
 	unsigned	length;