wifi: rtw89: introduce entity mode and its recalculated prototype

After supporting more than one channel, we need entity mode to decide
how to set current channel(s) on the sub-entities. This decision may
happen on set_channel() and rtw89_core_set_chip_txpwr().

For now, we support single one channel and use only first HW entry,
i.e. RTW89_SUB_ENTITY_0, RTW89_MAC_0, RTW89_PHY_0. Without something
unexpected, the entity mode should always be RTW89_ENT_MODE_SCC after
recalcated, where SCC means single channel concurrency. So, an assert
is added in set_channel() and rtw89_core_set_chip_txpwr().

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/20220809104952.61355-11-pkshih@realtek.com