err.h: move IOMEM_ERR_PTR() to err.h

Since IOMEM_ERR_PTR() macro deals with an error pointer, a better place
for it is err.h. This helps avoid dependency on io.h for the users that
don't need it.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Author: raagjadav

include/linux/err.h

@@ -44,6 +44,9 @@ static inline void * __must_check ERR_PTR(long error)
 /* Return the pointer in the percpu address space. */
 #define ERR_PTR_PCPU(error) ((void __percpu *)(unsigned long)ERR_PTR(error))
 
+/* Cast an error pointer to __iomem. */
+#define IOMEM_ERR_PTR(error) (__force void __iomem *)ERR_PTR(error)
+
 /**
  * PTR_ERR - Extract the error code from an error pointer.
  * @ptr: An error pointer.

include/linux/io.h

@@ -65,8 +65,6 @@ static inline void devm_ioport_unmap(struct device *dev, void __iomem *addr)
 }
 #endif
 
-#define IOMEM_ERR_PTR(err) (__force void __iomem *)ERR_PTR(err)
-
 void __iomem *devm_ioremap(struct device *dev, resource_size_t offset,
 			   resource_size_t size);
 void __iomem *devm_ioremap_uc(struct device *dev, resource_size_t offset,