staging: fieldbus: arcx-anybus: change custom -> mmio regmap

The arcx-anybus's registers are accessed via a memory-mapped
IO region. A regmap associated with this region is created
using custom reg_read() / reg_write() callbacks.

However, an abstraction which creates a memory-mapped IO
region backed regmap already exists: devm_regmap_init_mmio().

Replace the custom regmap with the existing kernel abstraction.
As a pleasant side-effect, sparse warnings now disappear.
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fieldbus/anybuss/arcx-anybus.c

@@ -111,49 +111,31 @@ static void export_reset_1(struct device *dev, bool assert)
  * at a time for now.
  */
 
-static int read_reg_bus(void *context, unsigned int reg,
-			unsigned int *val)
-{
-	void __iomem *base = context;
-
-	*val = readb(base + reg);
-	return 0;
-}
-
-static int write_reg_bus(void *context, unsigned int reg,
-			 unsigned int val)
-{
-	void __iomem *base = context;
-
-	writeb(val, base + reg);
-	return 0;
-}
+static const struct regmap_config arcx_regmap_cfg = {
+	.reg_bits = 16,
+	.val_bits = 8,
+	.max_register = 0x7ff,
+	.use_single_read = true,
+	.use_single_write = true,
+	/*
+	 * single-byte parallel bus accesses are atomic, so don't
+	 * require any synchronization.
+	 */
+	.disable_locking = true,
+};
 
 static struct regmap *create_parallel_regmap(struct platform_device *pdev,
 					     int idx)
 {
-	struct regmap_config regmap_cfg = {
-		.reg_bits = 11,
-		.val_bits = 8,
-		/*
-		 * single-byte parallel bus accesses are atomic, so don't
-		 * require any synchronization.
-		 */
-		.disable_locking = true,
-		.reg_read = read_reg_bus,
-		.reg_write = write_reg_bus,
-	};
 	struct resource *res;
 	void __iomem *base;
 	struct device *dev = &pdev->dev;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, idx + 1);
-	if (resource_size(res) < (1 << regmap_cfg.reg_bits))
-		return ERR_PTR(-EINVAL);
 	base = devm_ioremap_resource(dev, res);
 	if (IS_ERR(base))
 		return ERR_CAST(base);
-	return devm_regmap_init(dev, NULL, base, &regmap_cfg);
+	return devm_regmap_init_mmio(dev, base, &arcx_regmap_cfg);
 }
 
 static struct anybuss_host *