[tests] Skip wasm/atomics64-stress test on pre-r6 MIPS32

MIPS32 doesn't have instructions to properly handle 64-bit atomic
instructions.

Skipping those test on MIPS64 simulator because they have flaky
TIMEOUT on buildbots.

Change-Id: I31511dfce70a933b9326a7c270509c5f31af743a
Reviewed-on: https://chromium-review.googlesource.com/c/1367450Reviewed-by: Stephan Herhut <herhut@chromium.org>
Commit-Queue: Predrag Rudic <prudic@wavecomp.com>
Cr-Commit-Position: refs/heads/master@{#58125}

test/mjsunit/mjsunit.status

@@ -570,6 +570,10 @@
   'regress/regress-752764': [SKIP],
   'regress/regress-779407': [SKIP],
   'harmony/bigint/regressions': [SKIP],
+
+  # Pre-r6 MIPS32 doesn't have instructions needed to properly handle 64-bit
+  # atomic instructions.
+  'wasm/atomics64-stress': [PASS, ['mips_arch_variant != r6', SKIP]],
 }],  # 'arch == mipsel or arch == mips'
 
 ##############################################################################
@@ -624,6 +628,11 @@
   'regress/regress-779407': [SKIP],
 }],  # 'arch == mips64el or arch == mips64'
 
+['(arch == mips64el or arch == mips64) and simulator_run', {
+  # Slow tests which have flaky timeout on simulator.
+  'wasm/atomics64-stress': [SKIP],
+}],  # '(arch == mips64el or arch == mips64) and simulator_run'
+
 ##############################################################################
 ['system == windows', {
   # TODO(mstarzinger): Too slow with turbo fan.