PPC64/s390x: re-enable I64Atomic test on ppc64/s390x

This reverts commit b8a5ae47.

Change-Id: If5953398586af66f827103326891f7b4b39b78d1
Reviewed-on: https://chromium-review.googlesource.com/c/1262999Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#56416}

test/cctest/cctest.status

@@ -352,11 +352,10 @@
 }],  # '(arch == mipsel or arch == mips64el or arch == mips or arch == mips64) and not simd_mips'
 
 ##############################################################################
-['arch == mipsel or arch == mips64el or arch == mips or arch == mips64 or arch == ppc or arch == ppc64 or arch == s390 or arch == s390x', {
+['arch == mipsel or arch == mips64el or arch == mips or arch == mips64', {
   # TODO(mips-team): Implement I64Atomic operations on MIPS
-  # TODO(ppc-team, s390-team): Implement I64Atomic operations on PPC/s390
   'test-run-wasm-atomics64/*': [SKIP],
-}],  # 'arch == mipsel or arch == mips64el or arch == mips or arch == mips64 or arch == ppc or arch == ppc64 or arch == s390 or arch == s390x'
+}],  # 'arch == mipsel or arch == mips64el or arch == mips or arch == mips64'
 
 ##############################################################################
 ['mips_arch_variant == r6', {