Becuase the board select menu in arch/arm/Kconfig is too big,
move the Orion5x board select menu to orion5x/Kconfig.
Move also common settings (CONFIG_SYS_CPU="arm926ejs" and
CONFIG_SYS_SOC="orion5x").
Signed-off-by: Masahiro Yamada
Cc: Albert ARIBAUD