wifi: rtw89: phy: make generic txpwr setting functions

wifi: rtw89: phy: make generic txpwr setting functions

Previously, we thought control registers or setting things for TX power
series may change according to chip. So, setting functions are implemented
chip by chip. However, until now, the functions keep the same among chips,
at least 8852A, 8852C, and 8852B. There is a sufficient number of chips to
share generic setting functions. So, we now remake them including TX power
by rate, TX power offset, TX power limit, and TX power limit RU as generic
ones in phy.c.

Besides, there are some code refinements in the generic ones, but almost
all of the logic doesn't change.

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/20220928084336.34981-5-pkshih@realtek.com