drm/i915: Use hweight8() for 8bit masks

Use hweight8() instead of hweight32() for 8bit masks. Doesn't actually
matter for us since the arch code will go for hweight32() anyway, but
maybe we stil want to do this for documentation purposes?

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190821173033.24123-5-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>