EncodeTests: use the correct align for bitStreamBufferOffset

When aligning the bitstreamBufferOffset,
minBitstreamBufferOffsetAlignment from the video caps should
be used instead of minBitstreamBufferSizeAlignment.

Fix AMD support on Windows as the 2 alignments have different
values.

Components: Vulkan

VK-GL-CTS issue: 5040

Affected tests:
dEQP-VK.video.encode.*

Change-Id: I58a4e91b6e7710e27a9a9653d32694f79146e144

external/vulkancts/modules/vulkan/video/vktVideoEncodeTests.cpp

@@ -1773,7 +1773,7 @@ tcu::TestStatus VideoEncodeTestInstance::iterate(void)
 	fillBuffer(videoDeviceDriver, videoDevice, encodeBufferAlloc, headersData[0].data(), headersData[0].size(), bitstreamBufferOffset);
 
 	// Move offset to accommodate header data
-	bitstreamBufferOffset = deAlign64(bitstreamBufferOffset + headersData[0].size(), videoCapabilities->minBitstreamBufferSizeAlignment);
+	bitstreamBufferOffset = deAlign64(bitstreamBufferOffset + headersData[0].size(), videoCapabilities->minBitstreamBufferOffsetAlignment);
 
 	const Unique<VkCommandPool> encodeCmdPool(makeCommandPool(videoDeviceDriver, videoDevice, encodeQueueFamilyIndex));
 	const Unique<VkCommandBuffer> firstEncodeCmdBuffer(allocateCommandBuffer(videoDeviceDriver, videoDevice, *encodeCmdPool, VK_COMMAND_BUFFER_LEVEL_PRIMARY));