Moved ticker timer to a PIT channel + adjusted namings

The timer which creates interrupts is now also done using one of the PIT
channels. Since also here no chaining is possible we still need to do
some bits in software, but 32-bit without prescaling is still better
than 16-bit with.

Also some code was moved around and naming conventions changes, since no
lptmr is used anymore, and calling both pit-timer would get confusing