kasan: export kasan_poison as GPL

KASAN uses EXPORT_SYMBOL_GPL for symbols whose exporting is only required
for KASAN tests when they are built as a module.

kasan_poison is one on those symbols, so export it as GPL.

Link: https://lkml.kernel.org/r/171d0b8b2e807d04cca74f973830f9b169e06fb8.1703188911.git.andreyknvl@google.comSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/kasan/shadow.c

@@ -145,7 +145,7 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init)
 
 	__memset(shadow_start, value, shadow_end - shadow_start);
 }
-EXPORT_SYMBOL(kasan_poison);
+EXPORT_SYMBOL_GPL(kasan_poison);
 
 #ifdef CONFIG_KASAN_GENERIC
 void kasan_poison_last_granule(const void *addr, size_t size)