i965/nir: Dot not assign direct uniform locations first for vec4-based shaders

i965/nir: Dot not assign direct uniform locations first for vec4-based shaders

In the vec4 backend we want uniform locations to be assigned consecutively
since that way the offsets produced by nir_lower_io are exactly what we
need to implement nir_intrinsic_load_uniform. Otherwise we would need a
mapping to match the output of nir_lower_io to the actual uniform registers
we need to use.

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>