rtw89: packet offload handler to avoid warning

Add a dummy function for packet offload to eliminate warning message
"c2h class 1 func 2 not support". This c2h is for debug purpose and
its presence itself can do the work, so further parsing won't be
required for now.

Signed-off-by: Po Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220401055043.12512-3-pkshih@realtek.com