kirkwood: use generic diag.sh

kirkwood: use generic diag.sh

This commit removes the target-specific diag.sh script. This way, the
generic one is used for the target, which uses DT-aliases to specify the
LEDs used.

Generic diag.sh allow to use different LEDs to indicate different states.
Non-red status LEDs for indicating boot and a running system.
Where possible, the red or orange LEDs are used to indicate failsafe
mode and a running upgrade.

Compile-tested: all target devices.
Run-tested: CheckPoint L-50

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
[remove unrelated cosmetic changes, rename some labels, add pogo_e02]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>