drm/i915: Remove struct dp_link_dpll

drm/i915: Remove struct dp_link_dpll

struct dp_link_dpll is a pointless wrapper around struct dpll.
Just store the desired link rate into struct dpll::dot and
we're done.

v2: Document the full divider as a proper decimal number on chv
    Nuke bogus eDP 1.4 comments for chv while at it

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220307233940.4161-9-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>