drm/i915: Use a table to initilize shared dplls

Use a table to store the per-platform shared dpll information in one
place. This way, there is no need for platform specific init funtions.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1457451987-17466-8-git-send-email-ander.conselvan.de.oliveira@intel.com