drm/i915/wopcm: Don't fail on WOPCM partitioning failure

We don't have to immediately fail on WOPCM partitioning, we can wait
until we will start programming WOPCM registers. This should give us
more options if we decide to restore fallback in case of GuC failures.

v3: 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>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190802184055.31988-7-michal.wajdeczko@intel.com