drm/i915: Move Valleyview DP DPLL divisor calc to intel_dp_set_clock v2

For DP pll settings, there is only two golden configs.  Instead of
running through the algorithm to determine it, hardcode the value and get it
determine in intel_dp_set_clock.

v2: Rework on the intel_limit compiler warning. (Jani)

Signed-off-by: Chon Ming Lee <chon.ming.lee@intel.com>
[danvet: Fix up checkpatch issues.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>