anv: disable VK_EXT_calibrated_timestamps when the timestamp register is unreadable
When running in a virtual context, the timestamp register is unreadable on Gen12+.
While we could work around this, that would result in very inaccurate results for an extension where the whole point is accuracy, so let's just disable the extension.
/cc @llandwerlin @jekstrand @jljusten
Edited by Eric Engestrom