ARM: integrator: split board select into AP/CP select and CM select

ARM: integrator: split board select into AP/CP select and CM select

Select integrator boards by the combination of platform select (AP/CP)
and core module select (CM720T, CM920T, ...).

This allows us to remove CONFIG_SYS_EXTRA_OPTIONS and make Kconfig
much cleaner.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Linus Walleij <linus.walleij@linaro.org>