Tidy up comments & remove commented out code.

Change-Id: I46dd5ce06f36362c6274511cd1531d93926aa9bc
diff --git a/vp9/vp9_iface_common.h b/vp9/vp9_iface_common.h
index ed0122c..95ab13f 100644
--- a/vp9/vp9_iface_common.h
+++ b/vp9/vp9_iface_common.h
@@ -75,7 +75,7 @@
 
   yv12->border  = (img->stride[VPX_PLANE_Y] - img->w) / 2;
 #if CONFIG_ALPHA
-  // For development purposes, force alpha to hold the same data a Y for now.
+  // For development purposes, force alpha to hold the same data as Y for now.
   yv12->alpha_buffer = yv12->y_buffer;
   yv12->alpha_width = yv12->y_width;
   yv12->alpha_height = yv12->y_height;