ys: initial addition, Boundary Devices board

ys: update to v2017.01
ys: update to v2017.03

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>

ys: ys_1g_defconfig add CONFIG_BLOCK_CACHE
ys_512m: ys_512m_defconfig add CONFIG_BLOCK_CACHE
ys: use common code for eth init
ys: eth.c now in common directory
ys: move misc_init_r/do_kbd to common
ys: move mmc_init/ dram_init/ overwrite_console/ common_board_init/ splash_screen_prepare/ board_cfb_skip to common
ys: don't define CONFIG_CMD_FBPANEL, no display
ys: keep GP_RESET_DSP_N high
ys: add  CONFIG_SPI_FLASH_GIGADEVICE: to defconfigs
ys: add CONFIG_SPI_FLASH_WINBOND
ys: fix eMMC voltage vccq to allows 1.8V
ys: add comment for ddr
ys: port to v2018.07

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