tools/virtio: replace "__auto_type" with "auto"

Replace one instance of "__auto_type" with "auto" in:

tools/virtio/linux/compiler.h

This file *does* include <linux/compiler_types.h> directly, so there
is no need to duplicate the definition.

Signed-off-by: H. Peter Anvin (Intel) <[e-mail]>

tools/virtio/linux/compiler.h

···
  */
 #define data_race(expr)							\
 ({									\
-	__auto_type __v = (expr);					\
+	auto __v = (expr);						\
 	__v;								\
 })