drm/i915: Kill duplicated cdclk readout code from i2c

drm/i915: Kill duplicated cdclk readout code from i2c

We have a slightly different way of readoing out the cdclk in
gmbus_set_freq(). Kill that and just call .get_display_clock_speed().

Also need to remove the GMBUSFREQ update from intel_i2c_reset() since
that gets called way too early. Let's do it in intel_modeset_init_hw()
instead, and also pull the initial vlv_cdclk_freq update there from
init_clock gating.

Signed-off-by: Ville Syrjälä <[email protected]>
Reviewed-by: Jesse Barnes <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>