drm/i915: Hide vlv_force_wake_{get, put}() in intel_uncore.c

That function isn't used outside this file anymore.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>