[dv/sram] initial fcov plan
[dv/sram] initial fcov plan

this PR adds the initial functional coverage plan for SRAM_CTRL.

Signed-off-by: Udi Jonnalagadda <790cd677b6a22a419ffcfe0eb4293d8866eb70c9@google.com>

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