panfrost: Move the blend shader cache at the device level
This way we can re-use it in the Vulkan driver instead of implementing our own cache.
@icecream95 I've extended the has_constants case so we can have 16 variants live instead of one.
This way we can re-use it in the Vulkan driver instead of implementing our own cache.
@icecream95 I've extended the has_constants case so we can have 16 variants live instead of one.