rtw88: 8723d: set ltecoex register address in chip_info

Since 8723D use different address of ltecoex register, this commit add a
new field in chip_info and fill proper address. Then, ltecoex_read_reg()
and ltecoex_reg_write() can use them to access ltecoex according to chip.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200512102621.5148-7-yhchuang@realtek.com