wifi: rtw89: phy: reset value of force TX power for MAC ID

The force TX power function is disabled, but the force TX power value is
preserved, causing misunderstand the behavior in debug. Clear all values.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250325031021.15619-1-pkshih@realtek.com