drm/i915: Remove redundant/wrong comments

drm/i915: Remove redundant/wrong comments

Remove the comment specifying the exact formulat for calculating
the DPLL frequency from the *_find_best_dpll() functions. Each
platform variant has its own way to calculate these and we have
the code already to do that. These comments are entirely redundant
and often even wrong so just get rid of them.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220307233940.4161-3-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>