This ops is used to parse RX descriptor to know the length of received
packet and containing PHY status. If PHY status is existing, the order is
RX descriptor, PHY status and then packet.

There are two types of PHY status, named CCK and OFDM. Their size are the
same, but formats are different.

struct ieee80211_rx_status is also filled depends on above information.
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200504105010.10780-3-yhchuang@realtek.com