This patch creates a new LED trigger that triggers whenever the CPU is
active.  It can be configured with module parameters to trigger on any
combination of user, nice, system, or iowait time, and defaults to
including user and system time but not nice or iowait time.  I've tested
it a bit, and it seems to work, but no guarantees.  It's diffed against
2.6.17-git25.

Signed-off-by: Thomas Tuttle <thinkinginbinary@gmail.com>