board: toradex: imx: Remove not needed env variables

board: toradex: imx: Remove not needed env variables

Remove not needed variables from environment and include config files.

 - setup variable used to be executed from some bootscript, however
   it's not required and there is no point on having this small helper
   here
 - boot_file, kernel_file, ip_dyn variables are not used anywhere
 - fdt_fixup variable is just set empty
 - defargs, vidargs variables used to be used from some bootscript,
   however there is no point on having it here and even old legacy
   bootscript can work without them
 - removed CONFIG_ENABLE_DDR_TRAINING_DEBUG, this is a leftover from
   some copy/paste

On colibri imx6ull/imx7 NAND module, remove consoleblank=0, this is
already the Linux kernel default therefore useless.

Various Linux Kernel command line options removed are not-existing
left-over that applied to some old NXP i.MX downstream branch

Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>