32-bit bus values shown signed, should be unsigned

[Tuukka Toivonen]

If I have eg. 5 bit bus and set it to 11111 binary, it will
show up as 31, that is, unsigned (in decimal base).

However if the bus width is 32 and I set it to 2^32-1,
it will show up as a negative number which is inconsistent
with the first case.

I believe the fix is easy: just treat the bus value unsigned.