soc: aspeed: fix Kconfig

Fixes build break:

scripts/kconfig/conf  --allnoconfig Kconfig
drivers/soc/Kconfig:24: 'menu' in different file than 'menu'
drivers/soc/aspeed/Kconfig:1: location of the 'menu'
drivers/Kconfig:233: 'menu' in different file than 'menu'
drivers/soc/aspeed/Kconfig:1: location of the 'menu'
<none>:34: syntax error

Signed-off-by: Patrick Venture <venture@google.com>
Signed-off-by: Olof Johansson <olof@lixom.net>