llvmpipe: improve setup shader names (for debugging)

llvmpipe: improve setup shader names (for debugging)

The setup shaders were composed of both a fs shader number and a variant
number. But since they aren't tied to a particular fragment shader, the
former was a fixed zero while the latter was also always zero because
it was never assigned. So, similar to what the fs code does, use a ever
increasing number to give it a more catchy name (unlike fragment shaders
though where this number is for each explicitly created shader, we just use
it for the implicitly created variants).
And while here, fix whitespace a bit.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>