Remove deprecated 'autoscr' command/variables

The more standard 'source' command provides identical functionality to
the autoscr command.

Environment variable names/values on the MVBC_P, MVBML7, kmeter1,
mgcoge, and km8xx boards are updated to no longer refernce 'autoscr'.

The 'autoscript' and 'autoscript_uname' environment variables are
also removed.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Acked-by: Andre Schwarz <andre.schwarz@matrix-vision.de>
Acked-by: Heiko Schocher <hs@denx.de>