layers: Simplify descriptor validation in DrawState
layers: Simplify descriptor validation in DrawState

Many descriptor validation helper functions were returning skipCall based on the potential for a bad update structure type. However, at the beginning of update validation, we validate that the update type is ok. Therefore, the other helper functions don't need to continually repeat this check, and can be simplified to return relevant values directly.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools