A few tests still fail on PYBLITE, and that's due to differences in the
available peripheral block numbers on the different MCUs (eg I2C(2)
exists on one, but it's I2C(3) on the other).

Initialisation of CAN objects should now behave as other peripheral
objects.

Fixes issue #2001.

Reported here: http://forum.micropython.org/viewtopic.php?f=2&t=845

Thanks to Henrik Sölver for this patch.