[lldb] Fix arm breakages from D130985

The kernel was rejecting sizeof(struct GPR) as it was not a multiple of
8. Add a padding field to fix that.

One also wonders whether "cpsr" is right register name for aarch64.

GitOrigin-RevId: b8985ba0adb5fd881bb301fbc79370b86396e658
diff --git a/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h b/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h
index 3e992ac..7f7c3ee 100644
--- a/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h
+++ b/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h
@@ -47,6 +47,7 @@
     uint64_t sp;    // x31
     uint64_t pc;    // pc
     uint32_t cpsr;  // cpsr
+    uint32_t pad;
   };
   LLVM_PACKED_END