Initial K20 fixes

Added the required gpio-irq enable/disable + fixed bus_frequency
Modified timer code

Timer/Wait timer
Some tab fixes
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
Added (deep)sleep

Pretty much copy pasta of KLxx sleep code with only tiny change
Merge pull request #264 from Sissors/master

K20 general and timer adjustments