Add descriptor for shadow map

gpu.h

@@ -31,10 +31,12 @@ typedef struct {
 	VkShaderModule floor_vert_shader;
 	VkShaderModule model_vert_shader;
 	VkShaderModule frag_shader;
+	VkDescriptorSetLayout floor_desc_set_layout;
 	VkDescriptorSetLayout desc_set_layout;
 	VkDescriptorPool desc_pool;
 	VkRenderPass shadow_pass;
 	VkRenderPass render_pass;
+	VkDescriptorSet floor_desc_sets[MAX_FRAMES_IN_FLIGHT];
 	VkPipelineLayout floor_pipeline_layout;
 	VkPipeline floor_pipeline;
 	VkPipelineLayout model_pipeline_layout;