corechecks: Remove GetDeviceExtensions helper

Change-Id: Iee2dd338d831972583e074f07f3a42fd39282b88
diff --git a/layers/descriptor_sets.cpp b/layers/descriptor_sets.cpp
index 85a0233..dd1e359 100644
--- a/layers/descriptor_sets.cpp
+++ b/layers/descriptor_sets.cpp
@@ -2207,8 +2207,8 @@
                     *error_msg = error_str.str();
                     return false;
                 }
-                if (device_data_->GetDeviceExtensions()->vk_khr_sampler_ycbcr_conversion) {
-                    ImageSamplerDescriptor *desc = (ImageSamplerDescriptor *)descriptors_[index + di].get();
+                if (device_data_->device_extensions.vk_khr_sampler_ycbcr_conversion) {
+                    ImageSamplerDescriptor *desc = (ImageSamplerDescriptor *)descriptors_[index].get();
                     if (desc->IsImmutableSampler()) {
                         auto sampler_state = device_data_->GetSamplerState(desc->GetSampler());
                         auto iv_state = device_data_->GetImageViewState(image_view);
@@ -2494,7 +2494,7 @@
             }
         }
     }
-    if (!GetDeviceExtensions()->vk_khr_maintenance1) {
+    if (!device_extensions.vk_khr_maintenance1) {
         // Track number of descriptorSets allowable in this pool
         if (pool_state->availableSets < p_alloc_info->descriptorSetCount) {
             skip |= log_msg(report_data, VK_DEBUG_REPORT_ERROR_BIT_EXT, VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_POOL_EXT,