drm/i915: Correctly handle error path in i915_gem_init_hw

drm/i915: Correctly handle error path in i915_gem_init_hw

In function gem_init_hw() we are calling uc_init_hw() but in case
of error later in function, we missed to call matching uc_fini_hw()

v2: pulled out from the series

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180605122443.23776-1-michal.wajdeczko@intel.com