drm/i915: Store the m2 divider as a whole in bxt_clk_div

Get rid of the pointless m2 int vs. frac split in bxt_clk_div
and just store the whole divider as one.

v2: Document the full divider as a proper decimal number

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220307233940.4161-5-ville.syrjala@linux.intel.com


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