PTB assumes that instance id to be 0 at start of tile, but hw would
not do that, we need to set it.

This fixes some Vulkan CTS tests that start to fails after some other
tests used an instance id.

So for example, before this commit for the following tests, executed
in that order, we got the following behaviour:

dEQP-VK.pipeline.vertex_input.multiple_attributes.binding_one_to_many.attributes.float.mat2.mat3 => Pass
dEQP-VK.draw.indexed_draw.draw_instanced_indexed_triangle_strip => Pass
dEQP-VK.pipeline.vertex_input.multiple_attributes.binding_one_to_many.attributes.float.mat2.mat3 => Fails

Part-of: <mesa!6766>