wifi: rtw89: fw: add debug message for unexpected secure firmware

If failed to load a non-secure firmware with a secure chip, it only throws
a unclear message:

   rtw89_8922ae 0000:03:00.0: parse fw header fail

To address this case simpler, add a message to point out this.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250217064308.43559-5-pkshih@realtek.com