[SCSI] st: add struct rq_map_data support

This adds struct rq_map_data and the array of pointers to store
fragment buffers to struct st_buffer.

This patch doesn't remove st_buf_fragment but the latter patch does.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Kai Makisara <Kai.Makisara@kolumbus.fi>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index b92712f..74748ab 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -44,6 +44,8 @@
 	int syscall_result;
 	struct st_request *last_SRpnt;
 	struct st_cmdstatus cmdstat;
+	struct page **reserved_pages;
+	struct rq_map_data map_data;
 	unsigned char *b_data;
 	unsigned short use_sg;	/* zero or max number of s/g segments for this adapter */
 	unsigned short sg_segs;		/* number of segments in s/g list */