c534 receivers don't have serial numbers and only can pair two devices

c534 are limited receivers. They don't have serial numbers and can only pair a limited number of devices.

There is special code to handle them that gives them a serial number of 0 (the integer) and pairing number of 6. Both cause problems.

idefix testing> ../bin/solaar -D /dev/hidraw10 show 99 solaar: error: 'int' object has no attribute 'lower'

This happens because 0 is not a string.

Setting the pairing number to 6 give a very false impression of the receiver.

A fix is in the works.