Other than most boards with DDR4 the ASUS ZenWiFi BT8 cannot use the
"comb" DDR calibration option and needs only the "ddr4" option set
instead.
Build TF-A SPIM-NAND with UBI as well as to boot from RAM with
mtk_uartboot for MT7988 with DDR4 RAM.
Signed-off-by: John Crispin <john@phrozen.org>