ram: aspeed: Rework kconfig options

Ensure the ASPEED related options are grouped together under the RAM
option when enabling support.

This also makes some minor grammar corrections and renames options so
they present cleanly in menuconfig.

There should be no functional change to the configuration or binary.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Dylan Hung <dylan_hung@aspeedtech.com>