sparc64: fix prototypes of reads[bwl]()

Conventions for readsl() are the same as for readl() - any __iomem
pointer is acceptable, both const and volatile ones being OK.  Same
for readsb() and readsw().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Andreas Larsson <andreas@gaisler.com> # Making sparc64 subject prefix

Author: Al Viro

arch/sparc/include/asm/io_64.h

@@ -250,19 +250,19 @@ void insl(unsigned long, void *, unsigned long);
 #define insw insw
 #define insl insl
 
-static inline void readsb(void __iomem *port, void *buf, unsigned long count)
+static inline void readsb(const volatile void __iomem *port, void *buf, unsigned long count)
 {
 	insb((unsigned long __force)port, buf, count);
 }
 #define readsb readsb
 
-static inline void readsw(void __iomem *port, void *buf, unsigned long count)
+static inline void readsw(const volatile void __iomem *port, void *buf, unsigned long count)
 {
 	insw((unsigned long __force)port, buf, count);
 }
 #define readsw readsw
 
-static inline void readsl(void __iomem *port, void *buf, unsigned long count)
+static inline void readsl(const volatile void __iomem *port, void *buf, unsigned long count)
 {
 	insl((unsigned long __force)port, buf, count);
 }