drm/xe/pf: Fix xe_gt_sriov_pf_config_print_available_ggtt()

This function is using internal helper pf_get_spare_ggtt() that
expects PF's master mutex to be locked. Fix that.

Fixes: ac6598ae

 ("drm/xe/pf: Add support to configure SR-IOV VFs")
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Piotr Piórkowski <piotr.piorkowski@intel.com>
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419141000.314-1-michal.wajdeczko@intel.com