PPC: [wasm-simd] Move i64x2.eq out of post mvp

Port 906b9644

Original Commit Message:

    This is merged into the proposal:
    https://github.com/WebAssembly/simd/issues/419#issuecomment-765675472.

R=zhin@chromium.org, joransiu@ca.ibm.com, junyan@redhat.com, midawson@redhat.com
BUG=
LOG=N

Change-Id: I801c4337e2ea4671ef82cb1244b8da251d56fc2f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2650242Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#72341}

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

@@ -2176,6 +2176,7 @@ void InstructionSelector::VisitInt64AbsWithOverflow(Node* node) {
   V(I64x2Add)              \
   V(I64x2Sub)              \
   V(I64x2Mul)              \
+  V(I64x2Eq)               \
   V(I32x4Add)              \
   V(I32x4AddHoriz)         \
   V(I32x4Sub)              \