powerpc: Fix fallout from sg_page() changes

Fix fallout from 18dabf473e15850c0dbc8ff13ac1e2806d542c15:

In file included from include/linux/dma-mapping.h:52,
                 from drivers/base/dma-mapping.c:10:
include/asm/dma-mapping.h: In function 'dma_map_sg':
include/asm/dma-mapping.h:288: error: 'struct scatterlist' has no member named 'page'
include/asm/dma-mapping.h:288: error: 'struct scatterlist' has no member named 'page'
include/asm/dma-mapping.h:288: error: 'struct scatterlist' has no member named 'page'
include/asm/dma-mapping.h:289: error: 'struct scatterlist' has no member named 'page'
include/asm/dma-mapping.h:290: error: 'struct scatterlist' has no member named 'page'
include/asm/dma-mapping.h: In function 'dma_sync_sg_for_cpu':
include/asm/dma-mapping.h:331: error: 'struct scatterlist' has no member named 'page'

drivers/scsi/ps3rom.c: In function 'fetch_to_dev_buffer':
drivers/scsi/ps3rom.c:150: error: 'struct scatterlist' has no member named 'page'

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>