xtensa: fix prefetch in the raw_copy_to_user

'from' is the input buffer, it should be prefetched with prefetch, not
prefetchw.

Tested-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/xtensa/include/asm/uaccess.h

@@ -245,7 +245,7 @@ raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 static inline unsigned long
 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	prefetchw(from);
+	prefetch(from);
 	return __xtensa_copy_user((__force void *)to, from, n);
 }
 #define INLINE_COPY_FROM_USER