bt: initial addition, Boundary Devices board

Two configurations bt2g and bt4g for two different memory layouts
bt.h: CONFIG_IPUV3_CLK 264000000
bt: rename J6/J7 to J12V/J5V
bt: use nitrogen6x clock.cfg/ddr-setup.cfg
bt: add CONFIG_CMD_GPIO
bt: explicit fbp_detect_i2c
bt: use boundary.h
bt: add CONFIG_SPI_FLASH_SPANSION
bt.h: use BD_CMA to specify cma= on cmd_line
bt: bt2g_defconfig add CONFIG_BLOCK_CACHE
bt4g: bt4g_defconfig add CONFIG_BLOCK_CACHE
bt: use common code for eth init
bt: eth.c now in common directory
bt: move misc_init_r/do_kbd to common
bt: move mmc_init/ dram_init/ overwrite_console/ common_board_init/ splash_screen_prepare/ board_cfb_skip to common
bt: use common 1066mhz_4x256mx16.cfg
bt: add  CONFIG_SPI_FLASH_GIGADEVICE: to defconfigs
bt: use common ddr scripts
bt: port to v2018.07

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

bt: update to v2017.01
bt: update to v2017.03

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