[arm64] Fix AssertStackConsistency.

The implementation temporarily modifies jssp to avoid needing a scratch
register, then restores it afterwards. However, the exception path
wasn't properly restoring the value.

With this patch, failures in this part of AssertStackConsistency get
reported properly (with backtrace and a BailoutReason).

BUG=

Review URL: https://codereview.chromium.org/1556993004

Cr-Commit-Position: refs/heads/master@{#33135}

src/arm64/macro-assembler-arm64.cc

@@ -1343,6 +1343,8 @@ void MacroAssembler::AssertStackConsistency() {
 
       // Avoid generating AssertStackConsistency checks for the Push in Abort.
       { DontEmitDebugCodeScope dont_emit_debug_code_scope(this);
+        // Restore StackPointer().
+        sub(StackPointer(), csp, StackPointer());
         Abort(kTheCurrentStackPointerIsBelowCsp);
       }