staging: comedi: s626: base_addr is a void __iomem *

The base_addr variable in struct s626_private is an ioremap'ed pci resource and should be void __iomem * not a void *.

This quiets a lot of sparse warings for the writel and readl calls like:

warning: incorrect type in argument 1 (different address spaces) expected void const volatile [noderef] <asn:2>*addr got void *<noident>

warning: incorrect type in argument 2 (different address spaces) expected void volatile [noderef] <asn:2>*addr
   got void *

---

index 7beb8f6..2354586 100644
@@ -120,7 +120,7 @@ static const struct s626_board s626_boards[] = {
 
 struct s626_private {
 	struct pci_dev *pdev;
-	void *base_addr;
+	void __iomem *base_addr;
 	int got_regions;
 	short allocatedBuf;
 	uint8_t ai_cmd_running;	/*  ai_cmd is running */