lavapipe: All-0 DeviceUUID is discouraged by specification

From https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VkPhysicalDeviceIDPropertiesKHR.html

Khronos' conformance testing can not guarantee that deviceUUID values are actually unique, so implementors should make their own best efforts to ensure this. In particular, hard-coded deviceUUID values, especially all-0 bits, should never be used.

(This has been added in 1.2.146, also see https://github.com/KhronosGroup/Vulkan-Docs/issues/1273#issuecomment-653734333)

https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/gallium/frontends/lavapipe/lvp_device.c#L846

vulkaninfo:

VkPhysicalDeviceDriverProperties:
---------------------------------
        driverID           = DRIVER_ID_MESA_LLVMPIPE
        driverName         = llvmpipe
        driverInfo         = Mesa 21.3.3 (LLVM 13.0.0)
        conformanceVersion = 0.0.0.0
...
VkPhysicalDeviceIDProperties:
-----------------------------
        deviceUUID      = 00000000-0000-0000-0000-000000000000
        driverUUID      = 00000000-0000-0000-0000-000000000000