drm/i915: Use adjusted_mode->clock in lpt_program_iclkip

lpt_program_iclkip() wants to know the pixel clock. It should get that
information from adjusted_mode, not crtc->mode.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>