drm/i915: Rework DPLL calculation parameters for Ironlake

Got Ironlake DPLL parameter table, which reflects the hardware
optimized values. So this one trys to list DPLL parameters for
different output types, should potential fix clock issue seen
on new Arrandale CPUs.

This fixes DPLL setting failure on one 1920x1080 dual channel
LVDS for Ironlake. Test has also been made on LVDS panels with
smaller size and CRT/HDMI/DP ports for different monitors on
their all supported modes.

Update:
- Change name of double LVDS to dual LVDS.
- Fix SSC 120M reference clock to use the right range.

Cc: CSJ <changsijay@gmail.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>