drm/i915: Remove intel_clock_t typedef

Just use "struct dpll" everywhere. That's actually shorter than
intel_clock_t.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1462353119-9738-1-git-send-email-ander.conselvan.de.oliveira@intel.com