fsl_rio: Add comments for sRIO registers.

Add some comments to make sRIO registers map better readable.
Signed-off-by: Shaohui Xie <b21989@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/sysdev/fsl_rio.c

@@ -117,44 +117,59 @@ struct rio_atmu_regs {
 };
 
 struct rio_msg_regs {
-	u32 omr;
-	u32 osr;
+	u32 omr;	/* 0xD_3000 - Outbound message 0 mode register */
+	u32 osr;	/* 0xD_3004 - Outbound message 0 status register */
 	u32 pad1;
-	u32 odqdpar;
+	u32 odqdpar;	/* 0xD_300C - Outbound message 0 descriptor queue
+			   dequeue pointer address register */
 	u32 pad2;
-	u32 osar;
-	u32 odpr;
-	u32 odatr;
-	u32 odcr;
+	u32 osar;	/* 0xD_3014 - Outbound message 0 source address
+			   register */
+	u32 odpr;	/* 0xD_3018 - Outbound message 0 destination port
+			   register */
+	u32 odatr;	/* 0xD_301C - Outbound message 0 destination attributes
+			   Register*/
+	u32 odcr;	/* 0xD_3020 - Outbound message 0 double-word count
+			   register */
 	u32 pad3;
-	u32 odqepar;
+	u32 odqepar;	/* 0xD_3028 - Outbound message 0 descriptor queue
+			   enqueue pointer address register */
 	u32 pad4[13];
-	u32 imr;
-	u32 isr;
+	u32 imr;	/* 0xD_3060 - Inbound message 0 mode register */
+	u32 isr;	/* 0xD_3064 - Inbound message 0 status register */
 	u32 pad5;
-	u32 ifqdpar;
+	u32 ifqdpar;	/* 0xD_306C - Inbound message 0 frame queue dequeue
+			   pointer address register*/
 	u32 pad6;
-	u32 ifqepar;
+	u32 ifqepar;	/* 0xD_3074 - Inbound message 0 frame queue enqueue
+			   pointer address register */
 	u32 pad7[226];
-	u32 odmr;
-	u32 odsr;
+	u32 odmr;	/* 0xD_3400 - Outbound doorbell mode register */
+	u32 odsr;	/* 0xD_3404 - Outbound doorbell status register */
 	u32 res0[4];
-	u32 oddpr;
-	u32 oddatr;
+	u32 oddpr;	/* 0xD_3418 - Outbound doorbell destination port
+			   register */
+	u32 oddatr;	/* 0xD_341c - Outbound doorbell destination attributes
+			   register */
 	u32 res1[3];
-	u32 odretcr;
+	u32 odretcr;	/* 0xD_342C - Outbound doorbell retry error threshold
+			   configuration register */
 	u32 res2[12];
-	u32 dmr;
-	u32 dsr;
+	u32 dmr;	/* 0xD_3460 - Inbound doorbell mode register */
+	u32 dsr;	/* 0xD_3464 - Inbound doorbell status register */
 	u32 pad8;
-	u32 dqdpar;
+	u32 dqdpar;	/* 0xD_346C - Inbound doorbell queue dequeue Pointer
+			   address register */
 	u32 pad9;
-	u32 dqepar;
+	u32 dqepar;	/* 0xD_3474 - Inbound doorbell Queue enqueue pointer
+			   address register */
 	u32 pad10[26];
-	u32 pwmr;
-	u32 pwsr;
-	u32 epwqbar;
-	u32 pwqbar;
+	u32 pwmr;	/* 0xD_34E0 - Inbound port-write mode register */
+	u32 pwsr;	/* 0xD_34E4 - Inbound port-write status register */
+	u32 epwqbar;	/* 0xD_34E8 - Extended Port-Write Queue Base Address
+			   register */
+	u32 pwqbar;	/* 0xD_34EC - Inbound port-write queue base address
+			   register */
 };
 
 struct rio_tx_desc {