layers: Make logicOp param validation conditional

- Only validate that VkPipelineColorBlendStateCreateInfo::logicOp is
  a valid VkLogicOp enumeration value when
  VkPipelineColorBlendStateCreateInfo::logicOpEnable is set to VK_TRUE.
- Remove redundant VkPipelineColorBlendStateCreateInfo validation (hand
  written code replaced by generated code).

Change-Id: I075c58342678219c5ed1dd5c401e0da2cea53232
2 files changed