kill an "unused variable" compiler warning

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@4153 a1c6a512-1295-4272-9138-f99709370657

apps/main.c

@@ -146,6 +146,8 @@ void init(void)
             power_off();
         /* "On" pressed or USB connected: proceed */
     }
+#else
+    (void)coldstart;
 #endif
 
     rc = ata_init();