Fix alignment in vpx_image without external allocation.

This restores behaviors prior to
<40c8fde Fix image width alignment. Enable ImageSizeSetting test.>.

BUG=b/64710201

Change-Id: I559557afe80d5ff5ea6ac24021561715068e7786
diff --git a/vpx/src/vpx_image.c b/vpx/src/vpx_image.c
index ebd3d7f..af7c529 100644
--- a/vpx/src/vpx_image.c
+++ b/vpx/src/vpx_image.c
@@ -112,10 +112,10 @@
   if (!img_data) {
     uint64_t alloc_size;
     /* Calculate storage sizes given the chroma subsampling */
-    align = xcs ? (1 << xcs) - 1 : 1;
-    w = (d_w + align - 1) & ~(align - 1);
-    align = ycs ? (1 << ycs) - 1 : 1;
-    h = (d_h + align - 1) & ~(align - 1);
+    align = (1 << xcs) - 1;
+    w = (d_w + align) & ~align;
+    align = (1 << ycs) - 1;
+    h = (d_h + align) & ~align;
 
     s = (fmt & VPX_IMG_FMT_PLANAR) ? w : bps * w / 8;
     s = (s + stride_align - 1) & ~(stride_align - 1);