[PATCH] Represent laptop_mode as jiffies internally

Make that the internal value for /proc/sys/vm/laptop_mode is stored as
jiffies instead of seconds.  Let the sysctl interface do the conversions,
instead of doing on-the-fly conversions every time the value is used.

Add a description of the fact that laptop_mode doubles as a flag and a
timeout to the comment above the laptop_mode variable.

Signed-off-by: Bart Samwel <bart@samwel.tk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>