fix ARM32 userspace pointer sign-extension when running on ARM64 kernel

[0222826398]

No description provided.

[0222826398]

• Issue: remote_* calls could fail (-EFAULT) when running 32-bit userspace lib on 64-bit kernel.
• Root cause: In 32-bit userspace, some pointers were written into 64-bit fields with sign-extension (e.g. 0xffffffffxxxxxxxx). On 64-bit kernel, the value was kept as-is and treated as invalid user address in
  copy_from_user.
• Fix: Normalize pointer packing to zero-extend via uintptr_t before casting to uint64_t in userspace argument packing path.
• Result: Prevents invalid high-address pointer values and restores stable remote_* behavior in this mixed 32-bit userspace / 64-bit kernel setup.
• Validation: Re-ran FastRPC smoke flow(only cpu side) on platform; failure path no longer reproduces.

[ekanshibu]

Please add proper commit text with Signed-off-by

[0222826398]

Hi @ekanshibu,
Thanks for the heads-up, done!