[ARM] Add a common typesafe __io implementation

As Al did for Versatile in 2ad4f86b60,
add a typesafe __io implementation for platforms to use.  Convert
platforms to use this new simple typesafe implementation.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/io.h

@@ -79,6 +79,14 @@ extern void __iounmap(volatile void __iomem *addr);
  */
 extern void __readwrite_bug(const char *fn);
 
+/*
+ * A typesafe __io() helper
+ */
+static inline void __iomem *__typesafe_io(unsigned long addr)
+{
+	return (void __iomem *)addr;
+}
+
 /*
  * Now, pick up the machine-defined IO definitions
  */