i965: Set nr_params to the number of uniform components in the VS/GS path.

i965: Set nr_params to the number of uniform components in the VS/GS path.

Both do_vs_prog and do_gs_prog initialize brw_stage_prog_data::nr_params to
the number of uniform *vectors* required by the shader rather than the number
of uniform components, contradicting the comment.  This is inconsistent with
what the state upload code and scalar path expect but it happens to work until
Gen8 because vec4_visitor interprets it as a number of vectors on construction
and later on overwrites its original value with the number of uniform
components referenced by the shader.

Also there's no need to add the number of samplers, they're not actually
passed in as uniforms.

Fixes a memory corruption issue on BDW with SIMD8 VS.

Cc: "10.5" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>