Fix memory allocation size in subgroups tests

Many subgroups test shaders are executed using std140 memory layout,
meaning a minimum stride of 16-bytes.  The common allocation path
assumes a packed layout and hence does not allocate sufficient buffer
for uint arrays, etc.
This change increases the allocation request size to address the issue.

Affects:
dEQP-VK.subgroups.*

Components: Vulkan

VK-GL-CTS Issue: 1593

Change-Id: I150cf0bb69029137a44c778c04cecbf2f61515ae
diff --git a/external/vulkancts/modules/vulkan/subgroups/vktSubgroupsTestsUtils.cpp b/external/vulkancts/modules/vulkan/subgroups/vktSubgroupsTestsUtils.cpp
index 410089f..f6f5d98 100644
--- a/external/vulkancts/modules/vulkan/subgroups/vktSubgroupsTestsUtils.cpp
+++ b/external/vulkancts/modules/vulkan/subgroups/vktSubgroupsTestsUtils.cpp
@@ -573,7 +573,7 @@
 								context.getDevice(), &bufferCreateInfo);
 		vk::VkMemoryRequirements req = getBufferMemoryRequirements(
 										   context.getDeviceInterface(), context.getDevice(), *m_buffer);
-		req.size *= 2;
+		req.size *= 4;
 		m_allocation = context.getDefaultAllocator().allocate(
 						   req, MemoryRequirement::HostVisible);
 		VK_CHECK(context.getDeviceInterface().bindBufferMemory(