lpc31xx: Ported drivers for ADC and PWM

Ported IO drivers for ADC and PWM channels.
Applied minor changes for fixing compilation
errors.

IMPORTANT: ADC driver is new one, but the PWM
is coming from:

https://github.com/embeddedprojects/gnublin-lpc3131-3.3.0

Signed-off-by: Luis Galdos <luisgaldos@gmail.com>