init: reduce rootwait polling interval time to 5ms

For several devices, the rootwait time is sensitive because it directly
affects booting time.  The polling interval of rootwait is currently
100ms.  To save unnessesary waiting time, reduce the polling interval to
5 ms.

[[email protected]: remove used-once #define]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jungseung Lee <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

init/do_mounts.c

@@ -588,7 +588,7 @@ void __init prepare_namespace(void)
 			saved_root_name);
 		while (driver_probe_done() != 0 ||
 			(ROOT_DEV = name_to_dev_t(saved_root_name)) == 0)
-			msleep(100);
+			msleep(5);
 		async_synchronize_full();
 	}