drm/i915: s/DP_PLL_FREQ_160MHZ/DP_PLL_FREQ_162MHZ/

The DP link frequency is 162MHz, not 160MHz. Rename the ILK eDP PLL
defines to match.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446146763-31821-11-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>