wifi: rtlwifi: drop pre_fill_tx_bd_desc() from HAL interface

Since 'pre_fill_tx_bd_desc()' is actually used for rtl8192ee only,
there is no need to maintain function pointer in 'struct rtl_hal_ops',
and 'rtl92ee_pre_fill_tx_bd_desc()' may be converted to static.
Compile tested only.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231016135925.129223-1-dmantipov@yandex.ru