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>

src/intel/vulkan/anv_private.h

@@ -1092,6 +1092,13 @@ struct anv_physical_device {
     /** True if we can use bindless access for samplers */
     bool                                        has_bindless_samplers;
 
+    /** True if we can read the GPU timestamp register
+     *
+     * When running in a virtual context, the timestamp register is unreadable
+     * on Gen12+.
+     */
+    bool                                        has_reg_timestamp;
+
     /** True if this device has implicit AUX
      *
      * If true, CCS is handled as an implicit attachment to the BO rather than