sh: Remove sh7757lcr board

This board has not been converted to CONFIG_DM by the deadline of v2020.01
and is missing other conversions which depend on this as well.  Remove it.

As this is the last SH4A board, remove that support as well.

Cc: Marek Vasut <marek.vasut+renesas@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>