io_uring: dont ifdef io_alloc_cache_kasan()

Use IS_ENABLED in io_alloc_cache_kasan() so at least it gets compile
tested without KASAN.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://lore.kernel.org/r/35e53e83f6e16478dca0028a64a6cc905dc764d3.1738087204.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/alloc_cache.h

@@ -8,18 +8,14 @@
  */
 #define IO_ALLOC_CACHE_MAX	128
 
-#if defined(CONFIG_KASAN)
-static inline void io_alloc_cache_kasan(struct iovec **iov, int *nr)
-{
-	kfree(*iov);
-	*iov = NULL;
-	*nr = 0;
-}
-#else
 static inline void io_alloc_cache_kasan(struct iovec **iov, int *nr)
 {
+	if (IS_ENABLED(CONFIG_KASAN)) {
+		kfree(*iov);
+		*iov = NULL;
+		*nr = 0;
+	}
 }
-#endif
 
 static inline bool io_alloc_cache_put(struct io_alloc_cache *cache,
 				      void *entry)