ARM: realview: select apropriate targets

Now that we have multiplatform support, let the RealView
defconfigs select all the RealView boards so we boot out of
the box like before. This updates both defconfigs.

Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>