Becuase the board select menu in arch/arm/Kconfig is too big,
move the Rmobile board select menu to rmobile/Kconfig.
Consolidate also common settings (CONFIG_SYS_CPU="armv7" and
CONFIG_SYS_SOC="rmobile").
Signed-off-by: Masahiro Yamada
Cc: Nobuhiro Iwamatsu