ARM: at91: remove no-MMU at91x40 support

As there is currently no-one to take care of this old !MMU target and as its
support in recent kernels is a bit rotten, remove this at91x40 support and the
board file associated with it (at91eb01).
There are modern ARM !MMU in Mainline now so this target is not interesting for
building tests anymore. It would be better to start from these modern ARM !MMU
platforms to reintroduce at91x40 support if needed.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>