uboot-imx

arm/km: move CONFIG_EXTRA_ENV_SETTINGS from board to km_arm file

Since all the boards define the same env settings, this simplifies
the board files.

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Holger Brunck <holger.brunck@keymile.com>
cc: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <wd@denx.de>
cc: Detlev Zundel <dzu@denx.de>
cc: Prafulla Wadaskar <prafulla@marvell.com>