Make the minidump processor correctly populate the CPU information string for Microsoft-style ARM64 minidumps

This affects the output of tools like minidump_stackwalk which currently
print out the hexadecimal representation of the architecture instead of
the "arm64" string.

BUG=780

Change-Id: Id1d9d65fa5f3509c8c6580e2e3042f7d682b52be
Reviewed-on: https://chromium-review.googlesource.com/c/1412004
Reviewed-by: Mike Frysinger <vapier@chromium.org>

src/processor/minidump_processor.cc

@@ -535,6 +535,7 @@ bool MinidumpProcessor::GetCPUInfo(Minidump *dump, SystemInfo *info) {
       break;
     }
 
+    case MD_CPU_ARCHITECTURE_ARM64:
     case MD_CPU_ARCHITECTURE_ARM64_OLD: {
       info->cpu = "arm64";
       break;