[MIPS] Workaround for a sparse warning in include/asm-mips/io.h

CKSEG1ADDR() returns unsigned int value on 32bit kernel. Cast it to
unsigned long to get rid of this warning:

include2/asm/io.h:215:12: warning: cast adds address space to expression (<asn:2>)

Signed-off-by: Atsushi Nemoto <[e-mail]>
Signed-off-by: Ralf Baechle <[e-mail]>

include/asm-mips/io.h

···
 		 */
 		if (__IS_LOW512(phys_addr) && __IS_LOW512(last_addr) &&
 		    flags == _CACHE_UNCACHED)
-			return (void __iomem *)CKSEG1ADDR(phys_addr);
+			return (void __iomem *)
+				(unsigned long)CKSEG1ADDR(phys_addr);
 	}
 
 	return __ioremap(offset, size, flags);