drm/i915: vlv: init only needed state during early power well enabling

During the initial power well enabling on the driver init/resume path
we can avoid initialzing part of the HW/SW state that will be
initialized anyway by the subsequent init/resume code. For some steps
like HPD initialization this redundancy is not only an overhead but an
actual problem, since they can't be run this early in the overall init
sequence.

Add a flag marking the init phase and skip reinitialzing state that is
not strictly necessary based on that.

This is also needed by the upcoming HPD init restructuring by Thierry
and Daniel.

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