drm/i915/wopcm: Try to use already locked WOPCM layout

If WOPCM layout is already locked in HW we shouldn't continue
with our own partitioning as it could be likely different and
we will be unable to enforce it and fail. Instead we should try
to reuse what is already programmed, maybe there will be a fit.

This should enable us to reload driver with slightly different
HuC firmware (or even without HuC) without need to reboot.

v2: reordered/rebased

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190816105501.31020-4-michal.wajdeczko@intel.com