configs: move CMD_MD5SUM definition to defconfigs

configs: move CMD_MD5SUM definition to defconfigs

Boards with an apparent need for the md5sum command had the connected
config symbol defined in their board header file.
Move this over to the respective defconfig files now that md5sum is
configured via Kconfig.
(This is a manual effort, which differs from moveconfig.py, not sure
who is right here. Boards except sandbox loose the md5sum command with
moveconfig.py, though it was explicitly mentioned in their config.h's)

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
[trini: migrate stih410-b2260]
Signed-off-by: Tom Rini <trini@konsulko.com>