freedreno/ir3: Enable PIPE_CAP_PACKED_UNIFORMS

freedreno/ir3: Enable PIPE_CAP_PACKED_UNIFORMS

This commit turns on the gallium cap and adds a pass to lower the
load_ubo intrinsics for block 0 back to load_uniform intrinsics and
adjust the backend where the cap switches units from vec4s to dwords.

As we stop using ir3_glsl_type_size() for uniform layout, this also
corrects an issue where we would allocate a vec4 slot for samplers in
uniforms, fixing:

  dEQP-GLES3.functional.shaders.struct.uniform.sampler_array_fragment
  dEQP-GLES3.functional.shaders.struct.uniform.sampler_array_vertex
  dEQP-GLES3.functional.shaders.struct.uniform.sampler_nested_fragment
  dEQP-GLES2.functional.shaders.struct.uniform.sampler_nested_vertex
  dEQP-GLES2.functional.shaders.struct.uniform.sampler_nested_fragment

Signed-off-by: Kristian H. Kristensen <hoegsberg@chromium.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>