dmaengine: shdma: Add more register documentation

Also add a few definitions that were missing.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
diff --git a/include/linux/sh_dma.h b/include/linux/sh_dma.h
index b7b43b8..56b97ee 100644
--- a/include/linux/sh_dma.h
+++ b/include/linux/sh_dma.h
@@ -95,19 +95,21 @@
 };
 
 /* DMAOR definitions */
-#define DMAOR_AE	0x00000004
+#define DMAOR_AE	0x00000004	/* Address Error Flag */
 #define DMAOR_NMIF	0x00000002
-#define DMAOR_DME	0x00000001
+#define DMAOR_DME	0x00000001	/* DMA Master Enable */
 
 /* Definitions for the SuperH DMAC */
-#define DM_INC	0x00004000
-#define DM_DEC	0x00008000
-#define DM_FIX	0x0000c000
-#define SM_INC	0x00001000
-#define SM_DEC	0x00002000
-#define SM_FIX	0x00003000
-#define CHCR_DE	0x00000001
-#define CHCR_TE	0x00000002
-#define CHCR_IE	0x00000004
+#define DM_INC	0x00004000	/* Destination addresses are incremented */
+#define DM_DEC	0x00008000	/* Destination addresses are decremented */
+#define DM_FIX	0x0000c000	/* Destination address is fixed */
+#define SM_INC	0x00001000	/* Source addresses are incremented */
+#define SM_DEC	0x00002000	/* Source addresses are decremented */
+#define SM_FIX	0x00003000	/* Source address is fixed */
+#define RS_AUTO	0x00000400	/* Auto Request */
+#define RS_ERS	0x00000800	/* DMA extended resource selector */
+#define CHCR_DE	0x00000001	/* DMA Enable */
+#define CHCR_TE	0x00000002	/* Transfer End Flag */
+#define CHCR_IE	0x00000004	/* Interrupt Enable */
 
 #endif