drm/xe/vf: Treat GMDID as another runtime register

While the GMDID registers are not part of the runtime register list
shared by the PF driver, we may still return cached values from our
VF specific read32() helper function.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240523192240.844-7-michal.wajdeczko@intel.com