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.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2797>