layers: Clean up poolMap access

Remove some unneeded passing of poolMap around and use getPoolNode()
function in DescriptorSet class.
diff --git a/layers/descriptor_sets.h b/layers/descriptor_sets.h
index 1b7ebb4..d53d97f 100644
--- a/layers/descriptor_sets.h
+++ b/layers/descriptor_sets.h
@@ -257,9 +257,7 @@
                                  const VkCopyDescriptorSet *);
 // Validate that Allocation state is ok
 bool ValidateAllocateDescriptorSets(const debug_report_data *, const VkDescriptorSetAllocateInfo *,
-                                    const std::unordered_map<VkDescriptorSetLayout, cvdescriptorset::DescriptorSetLayout *> &,
-                                    const std::unordered_map<VkDescriptorPool, DESCRIPTOR_POOL_NODE *> &,
-                                    AllocateDescriptorSetsData *);
+                                    const core_validation::layer_data *, AllocateDescriptorSetsData *);
 // Update state based on allocating new descriptorsets
 void PerformAllocateDescriptorSets(const VkDescriptorSetAllocateInfo *, const VkDescriptorSet *, const AllocateDescriptorSetsData *,
                                    std::unordered_map<VkDescriptorPool, DESCRIPTOR_POOL_NODE *> *,