DMAENGINE: ste_dma40: removed a few magic numbers

Make sure to extract the revision field explicitly and document
what bits are being accessed here without magic numbers.

Signed-off-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dma/ste_dma40_ll.h b/drivers/dma/ste_dma40_ll.h
index 0c468c3..7a6acec 100644
--- a/drivers/dma/ste_dma40_ll.h
+++ b/drivers/dma/ste_dma40_ll.h
@@ -163,6 +163,9 @@
 #define D40_DREG_PERIPHID0	0xFE0
 #define D40_DREG_PERIPHID1	0xFE4
 #define D40_DREG_PERIPHID2	0xFE8
+#define D40_DREG_PERIPHID2_REV_POS 4
+#define D40_DREG_PERIPHID2_REV_MASK (0xf << D40_DREG_PERIPHID2_REV_POS)
+#define D40_DREG_PERIPHID2_DESIGNER_MASK 0xf
 #define D40_DREG_PERIPHID3	0xFEC
 #define D40_DREG_CELLID0	0xFF0
 #define D40_DREG_CELLID1	0xFF4