drm/i915: Remove locks around skl+ scaler programming

All the skl+ scaler registers are suitably confined to their own
cachelines so we don't need the uncore.lock to globally serialize
access to these registers. We actually already dropped some of this
in commit 14ad1529

 ("drm/i915: Make skl+ universal plane
registers unlocked") as the plane scaler enabling/reconfiguration
became lockless. So let's complete that and remove the rest of
the locks from the scaler programming as well.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220224165103.15682-2-ville.syrjala@linux.intel.com
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>