Currently the cpu/lpc2387 init code hard-codes a 16 MHz
external oscillator.
Instead, calculate the PLL multiplier based on the board define
and also allow to run without an external oscillator.
This PR converts tabs to white spaces.
The statement I used for the conversion:
```find . -name "*.[ch]" -exec zsh -c 'expand -t 4 "$0" > /tmp/e && mv /tmp/e "$0"' {} \;```
Afterwards, I had a quick overview of the converted files to prevent odd indentation.
