[flash_ctrl] RTL fix for DC elab failure
[flash_ctrl] RTL fix for DC elab failure

Fixes #12306

Signed-off-by: Michael Schaffner <a005a2d3342a687ea2d05360c953107acbe83e08@opentitan.org>

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