pwm.hpp: Pwm constructor optional arg order change
pwm.hpp: Pwm constructor optional arg order change

This means that you can initialise a non raw Pwm pin without having to redefine
chipid as -1 (anything but -1 enables raw mode for Pwm)

Fixes #93.

Signed-off-by: Brendan Le Foll <3e0e8c4069934e8b47d99704927a85c66c0ceb33@intel.com>

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