ARM: lh7a40x: remove unmaintained platform support

lh7a40x has only been receiving updates for updates to generic code.
The last involvement from the maintainer according to the git logs was
in 2006.  As such, it is a maintainence burden with no benefit.

This gets rid of two defconfigs.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>