[PARISC] Fix iounmap compile warning

iounmap's argument needs to be both const and volatile, otherwise we'll
get warnings that we're discarding pointer qualifiers
Signed-off-by: NMatthew Wilcox <matthew@wil.cx>
Signed-off-by: NKyle McMartin <kyle@parisc-linux.org>

arch/parisc/mm/ioremap.c

@@ -188,7 +188,7 @@ void __iomem * __ioremap(unsigned long phys_addr, unsigned long size, unsigned l
 }
 EXPORT_SYMBOL(__ioremap);
 
-void iounmap(void __iomem *addr)
+void iounmap(const volatile void __iomem *addr)
 {
 	if (addr > high_memory)
 		return vfree((void *) (PAGE_MASK & (unsigned long __force) addr));

include/asm-parisc/io.h

@@ -134,7 +134,7 @@ extern inline void __iomem * ioremap(unsigned long offset, unsigned long size)
 }
 #define ioremap_nocache(off, sz)	ioremap((off), (sz))
 
-extern void iounmap(void __iomem *addr);
+extern void iounmap(const volatile void __iomem *addr);
 
 static inline unsigned char __raw_readb(const volatile void __iomem *addr)
 {