Fix ASTC framework tests
Fix ASTC framework tests

CEMS test mode will generate HDR blocks so trying to validate that it
generates valid LDR blocks will fail.

Change-Id: If9294d429811054e38167ba942f6910ad2545820

KhronosGroup/VK-GL-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,chadversary/deqp,chadversary/deqp,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,chadversary/deqp,chadversary/deqp,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,chadversary/deqp,googlestadia/VK-GL-CTS