broadcom/compiler: always enable per-quad on spill operations
This ensures that any channels used for helper invocations are also spilled/filled correctly.
Alternatively, we could recursively track all temps that get involved in computing values that are then used in explicit (dfdx,dfdy) or implicit (texture coordinates for mipmap or anisotropic filtering, etc) derivatives, and only-enable per-quad on these (or disable spilling of any of these values).
Fixes: dEQP-VK.graphicsfuzz.cov-dfdx-dfdy-after-nested-loops