drm/i915: cleanup per-pipe reg usage

We had some conversions over to the _PIPE macros, but didn't get
everything.  So hide the per-pipe regs with an _ (still used in a few
places for legacy) and add a few _PIPE based macros, then make sure
everyone uses them.

[update: remove usage of non-existent no-op macro]
[update 2: keep modesetting suspend/resume code, update to new reg names]
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[ickle: stylistic cleanups for checkpatch and taste]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index d2fdfd5..29fb217 100644
--- a/drivers/gpu/drm/i915/intel_overlay.c
+++ b/drivers/gpu/drm/i915/intel_overlay.c
@@ -255,7 +255,7 @@
 		return 0;
 
 	/* most i8xx have pipe a forced on, so don't trust dpms mode */
-	if (I915_READ(PIPEACONF) & PIPECONF_ENABLE)
+	if (I915_READ(_PIPEACONF) & PIPECONF_ENABLE)
 		return 0;
 
 	crtc_funcs = crtc->base.helper_private;