[wasm simd] Fix two reversing swizzles.

- Fixes bugs in x64 and ia32 reversing swizzles.

Change-Id: Iea0beccab804fd8e68dc58bc0fa11db46ac391c1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1330104
Commit-Queue: Bill Budge <bbudge@chromium.org>
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62900}

src/compiler/backend/ia32/instruction-selector-ia32.cc

@@ -2259,13 +2259,13 @@ static const ShuffleEntry arch_shuffles[] = {
     {{7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, 8},
      kSSES8x8Reverse,
      kAVXS8x8Reverse,
-     false,
-     false},
+     true,
+     true},
     {{3, 2, 1, 0, 7, 6, 5, 4, 11, 10, 9, 8, 15, 14, 13, 12},
      kSSES8x4Reverse,
      kAVXS8x4Reverse,
-     false,
-     false},
+     true,
+     true},
     {{1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14},
      kSSES8x2Reverse,
      kAVXS8x2Reverse,

src/compiler/backend/x64/instruction-selector-x64.cc

@@ -2997,12 +2997,12 @@ static const ShuffleEntry arch_shuffles[] = {
      true},
     {{7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, 8},
      kX64S8x8Reverse,
-     false,
-     false},
+     true,
+     true},
     {{3, 2, 1, 0, 7, 6, 5, 4, 11, 10, 9, 8, 15, 14, 13, 12},
      kX64S8x4Reverse,
-     false,
-     false},
+     true,
+     true},
     {{1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14},
      kX64S8x2Reverse,
      true,