rtw88: use rtw_phy_pg_cfg_pair struct, not arrays

Use proper struct for BB PG tables.

TODO: we need to find a way to store the tables that have
      condition values.

Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>