mesa: Fill Parameter storage indices even when not using SPIR-V

mesa: Fill Parameter storage indices even when not using SPIR-V

When creating Parameters, fill in the associated uniform storage
indices, like it is done with the NIR linker used for SPIR-V.  This
will allow later code to not rely on names (which would never work for
SPIR-V where names are optional).

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>