alpha: Replace one-element array with flexible array member

Replace the deprecated one-element array with a modern flexible array
member in the struct crb_struct.

Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Matt Turner <mattst88@gmail.com>

Author: toblux

arch/alpha/include/asm/hwrpb.h

@@ -135,7 +135,7 @@ struct crb_struct {
 	/* virtual->physical map */
 	unsigned long map_entries;
 	unsigned long map_pages;
-	struct vf_map_struct map[1];
+	struct vf_map_struct map[];
 };
 
 struct memclust_struct {