wifi: rtw89: re-arrange channel related stuffs under HAL

We are planning to support mac80211 chanctx. To reduce future works,
the driver architecture is adjusted first to isolate related things.

According to chip, our HW may have multiple sub-entities to support
multiple mac80211 chanctx. Struct rtw89_chan has been introduced for
things about channel/band/subband/... Now introduce struct rtw89_chan_rcd
to record difference after assigning new one of struct rtw89_chan.

We will implement and support chanctx with single channel first, i.e.
only use entry in RTW89_SUB_ENTITY_0, before handling dual channels.

Our hierarchy in planning will become as the following.
DEV
-> HAL
---> entity (manage status across sub-entities)
-----> sub-entity[*] (support mac80211 chanctx)
where each sub-entity contains one struct rtw89_chan.

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/20220809104952.61355-4-pkshih@realtek.com