nomadik: kconfig: move board select menu and common settings

Becuase the board select menu in arch/arm/Kconfig is too big,
move the Nomadik board select menu to nomadik/Kconfig.

Move also common settings (CONFIG_SYS_CPU="arm926ejs" and
CONFIG_SYS_SOC="nomadik").

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>