openrd: Once again shrink binary size

With some recent changes to relevant drivers here the openrd board
(openrd_client in this case) does not fit within its size constraint.
We can however drop the slightly extended baudrate table and then the
duplication of mtdparts/mtdids in the default environment.  These
defaults are set in the environment by the 'mtdparts' command and
otherwise referenced throughout the code.

Signed-off-by: Tom Rini <trini@konsulko.com>