drm/i915: Remove bxt m2_frac_en

Remove the pointless m2_frac_en from bxt_clk_div.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220301173128.6988-6-ville.syrjala@linux.intel.com


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