ARM: warnings in arch/arm/include/asm/uaccess.h

On NOMMU ARM, the __addr_ok() and __range_ok() macros do not evaluate
their arguments, which may lead to harmless build warnings in some
code where the variables are not used otherwise. Adding a cast to void
gets rid of the warning and does not make any semantic changes.

Without this patch, building at91x40_defconfig results in:

fs/read_write.c: In function 'rw_copy_check_uvector':
fs/read_write.c:684:9: warning: unused variable 'buf' [-Wunused-variable]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/uaccess.h

@@ -200,8 +200,8 @@ extern int __put_user_8(void *, unsigned long long);
 #define USER_DS			KERNEL_DS
 
 #define segment_eq(a,b)		(1)
-#define __addr_ok(addr)		(1)
-#define __range_ok(addr,size)	(0)
+#define __addr_ok(addr)		((void)(addr),1)
+#define __range_ok(addr,size)	((void)(addr),0)
 #define get_fs()		(KERNEL_DS)
 
 static inline void set_fs(mm_segment_t fs)