ash2: KEY_COL0 must be UART4_TX_DATA
ash2: add power_init_board because mdelay cannot be used in board_early_init_f
ash2: use common 800mhz_4x128mx16.cfg, and calibrate ddr
ash2: rgb24 vs rgb66 panel have different backlight active levels
ash2: fixup dtb backlight levels
ash2: add  CONFIG_SPI_FLASH_GIGADEVICE: to defconfigs
ash2: use common ddr script
ash2: port to v2018.07

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>