[otbn] Add ram_cfg_i port in testbench
[otbn] Add ram_cfg_i port in testbench

It's an unused signal, but we should still connect all ports in the port
list.

Signed-off-by: Philipp Wagner <5a4b10454c30419e54a1570be358a516ff84bb63@lowrisc.org>

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