drm/i915: move encoder pre enable hooks togther on ilk+

The ->pre_enable hook is only used for the cpu edp port on ilk-ivb, so
we can safely move it up across the fdi pll enabling.

Unfortunately we can't (yet) merge in the pre_pll enable hook despite
that only lvds uses it on ilk-ivb: Since the same lvds hook is also
need on i9xx platforms we need to fix up the pll enabling sequence
there, too.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>