Fix extension check in transform feedback tests

Check support for VK_EXT_transform_feedback extension before checking
if transformFeedback feature is supported.

Affects:
dEQP-VK.transform_feedback.simple.*

Components: Vulkan

VK-GL-CTS issue: 3697

Change-Id: I478669a0c4f4e0a88ab2161f926d39186f719585
diff --git a/external/vulkancts/modules/vulkan/transform_feedback/vktTransformFeedbackSimpleTests.cpp b/external/vulkancts/modules/vulkan/transform_feedback/vktTransformFeedbackSimpleTests.cpp
index 5c374ea..c1f7456 100644
--- a/external/vulkancts/modules/vulkan/transform_feedback/vktTransformFeedbackSimpleTests.cpp
+++ b/external/vulkancts/modules/vulkan/transform_feedback/vktTransformFeedbackSimpleTests.cpp
@@ -459,7 +459,6 @@
 	void											verifyTransformFeedbackBuffer	(const MovePtr<Allocation>& bufAlloc,
 																					 const deUint32 bufBytes);
 
-	const bool										m_extensions;
 	const VkExtent2D								m_imageExtent2D;
 	const TestParameters							m_parameters;
 	VkPhysicalDeviceTransformFeedbackPropertiesEXT	m_transformFeedbackProperties;
@@ -468,7 +467,6 @@
 
 TransformFeedbackTestInstance::TransformFeedbackTestInstance (Context& context, const TestParameters& parameters)
 	: TestInstance		(context)
-	, m_extensions		(context.requireDeviceFunctionality("VK_EXT_transform_feedback"))
 	, m_imageExtent2D	(makeExtent2D(IMAGE_SIZE, IMAGE_SIZE))
 	, m_parameters		(parameters)
 	, m_rnd				(0)
@@ -2378,6 +2376,8 @@
 
 void TransformFeedbackTestCase::checkSupport (Context& context) const
 {
+	context.requireDeviceFunctionality("VK_EXT_transform_feedback");
+
 	if (context.getTransformFeedbackFeaturesEXT().transformFeedback == VK_FALSE)
 		TCU_THROW(NotSupportedError, "transformFeedback feature is not supported");