Block device LED trigger.

Make a read/write/readwrite LED trigger for each block device.

Use blk transferred sector statistics to trigger leds. Only sectors
completed are taken into account.

The current mmc trigger uses low-level knowledge of the driver so it can
eg. keep the led lit when requests get stuck. The requests pending field
could be used for similar effect but there is only one field for both
reads and writes.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Make ledtrig-block loadable.

Fix issues with loading/unloading the block led trigger.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Add led trigger activation callbacks.

Notify trigger when it's in use so that trigger timer can be
enabled/disabled.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Split out private led trigger headers.

No need for linux/leds.h to contain trigger-specific bits.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Remove ide disk trigger.

Unlike mmc or nand trigger this trigger is rather stupid and block
tigger can providy equivalent functionality for any block device
regardless of hardware.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>