s390/kasan: fix strncpy_from_user kasan checks

arch/s390/lib/uaccess.c is built without kasan instrumentation. Kasan
checks are performed explicitly in copy_from_user/copy_to_user
functions. But since those functions could be inlined, calls from
files like uaccess.c with instrumentation disabled won't generate
kasan reports. This is currently the case with strncpy_from_user
function which was revealed by newly added kasan test. Avoid inlining of
copy_from_user/copy_to_user when the kernel is built with kasan support
to make sure kasan checks are fully functional.
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/uaccess.h

@@ -55,8 +55,10 @@ raw_copy_from_user(void *to, const void __user *from, unsigned long n);
 unsigned long __must_check
 raw_copy_to_user(void __user *to, const void *from, unsigned long n);
 
+#ifndef CONFIG_KASAN
 #define INLINE_COPY_FROM_USER
 #define INLINE_COPY_TO_USER
+#endif
 
 #ifdef CONFIG_HAVE_MARCH_Z10_FEATURES