nouveau: Stop using hex for SM numbers

nouveau: Stop using hex for SM numbers

There's no indication that NVIDIA considers this to be anything other
than a decimal number.  Much to the contrary, the number of 5s and 9s in
the SM number table implies they very much are base 10.  Given that
Lovelace is SM90, we'll likely be hitting 100 fairly soon at which point
this will stop fitting in a uint8_t.  Switch to decimal to compress it
down a bit.

Also, rename the field to SM which beter matches the NVIDIA docs and
ensures that there are no users of this which are likely to be confused.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24326>