drm/i915/gt: Re-work intel_write_status_page

Re-work intel_write_status_page to use drm_clflush_virt_range. This
will prevent compiler errors when building for non-x86 architectures.

Signed-off-by: Michael Cheng <michael.cheng@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220321223819.72833-2-michael.cheng@intel.com