Fix valid usage violation in vkFreeDescriptorSets

The descriptor pool used in vkFreeDescriptorSets was not created with
the VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT flag, resulting a
valid usage check failed in the driver. Adding the flags fixes the
issue.

Affects:
dEQP-VKSC.sc.device_object_reservation.limits.request_count.*

Componnets:
VulkanSC

Change-Id: Id5ecff4c58478c13aaf035eaff07554c3260abf0
diff --git a/external/vulkancts/modules/vulkan/sc/vktDeviceObjectReservationTests.cpp b/external/vulkancts/modules/vulkan/sc/vktDeviceObjectReservationTests.cpp
index 967823b..b536d8c 100644
--- a/external/vulkancts/modules/vulkan/sc/vktDeviceObjectReservationTests.cpp
+++ b/external/vulkancts/modules/vulkan/sc/vktDeviceObjectReservationTests.cpp
@@ -712,7 +712,7 @@
 		{
 			VK_STRUCTURE_TYPE_DESCRIPTOR_POOL_CREATE_INFO,					// sType
 			DE_NULL,														// pNext
-			(VkDescriptorPoolCreateFlags)0u,								// flags
+			VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT,				// flags
 			maxSets,														// maxSets
 			1u,																// poolSizeCount
 			&poolSizes,														// pPoolSizes