[dv] Override mem with info in the top hjson for RAL
[dv] Override mem with info in the top hjson for RAL

Address ral model issue in #7218

We have 2 types of sram in top_earlgrey. we use memory size from sram
block level hjson to create ral model. now we want to override the memory
size with in the top hjson. This PR enables this support

Signed-off-by: Weicai Yang <4fa8c7762ee4da95e3dee7dae2c3263ea16637f9@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan