wifi: rtl8xxxu: Make RTL8192CU, RTL8723AU TX with 40 MHz width

wifi: rtl8xxxu: Make RTL8192CU, RTL8723AU TX with 40 MHz width

Set the required fields in the TX descriptor to allow these chips to
transmit with 40 MHz channel width when the access point supports it.

Tested only with RTL8192CU, but these settings are identical for
RTL8723AU.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/30d95228-69b2-48f9-8854-c98d2408c4d3@gmail.com