s2io: Fix warnings due to -Wunused-but-set-variable.

Most of these are cases where we are trying to read back a register
after a write to ensure completion.

Simply pre-fixing the readl() or readq() with "(void)" is sufficient
because these are volatile operations and the compiler cannot eliminate
them just because no real assignment takes place.

The case of free_rxd_blk()'s assignments to "struct buffAdd *ba" is a
real spurious assignment as this variable is completely otherwise
unused.

Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Jon Mason <jdmason@kudzu.us>
diff --git a/drivers/net/s2io.h b/drivers/net/s2io.h
index 628fd27..800b3a4 100644
--- a/drivers/net/s2io.h
+++ b/drivers/net/s2io.h
@@ -1002,18 +1002,16 @@
 #define LF	2
 static inline void SPECIAL_REG_WRITE(u64 val, void __iomem *addr, int order)
 {
-	u32 ret;
-
 	if (order == LF) {
 		writel((u32) (val), addr);
-		ret = readl(addr);
+		(void) readl(addr);
 		writel((u32) (val >> 32), (addr + 4));
-		ret = readl(addr + 4);
+		(void) readl(addr + 4);
 	} else {
 		writel((u32) (val >> 32), (addr + 4));
-		ret = readl(addr + 4);
+		(void) readl(addr + 4);
 		writel((u32) (val), addr);
-		ret = readl(addr);
+		(void) readl(addr);
 	}
 }