wifi: rtw89: fix parsing offset for MCC C2H

A 8-byte offset is missed during parsing C2Hs (chip to host packets)
of MCC (multi-channel concurrent) series.
So, we fix it.

Fixes: ef9dff4c ("wifi: rtw89: mac: process MCC related C2H")
Signed-off-by: Zong-Zhe Yang <kevin_yang@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/20230119064342.65391-1-pkshih@realtek.com