anv: Fix get_image_format_properties() - ASTC
Teach it to calculate the format features for ASTC. The goal is to incrementally fix get_image_format_properties() to return a correct result. Currently, it returns incorrect VkFormatFeatureFlags which the caller must clean up. v2: New commit message Reviewed-by: Jason Ekstrand <jason@jlekstrand.net> (v1)