drm/xe/vf: Catch all unexpected register reads

While we can only mimic read32 for a few GT registers for which
the PF shared the values, we shouldn't avoid calling helper code
if we try to access non-GT register, as then we miss to trigger
a debug warning. For cases where sriov_vf_gt was not set, just
use primary_gt instead.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250311135726.1998-3-michal.wajdeczko@intel.com