This adds some optimizations to serv_rf_ram_if. It also adds a read enable
signal and delays writes one cycle which has the added bonus that no reads
or writes happen in the same cycle for RF_WIDTH > 2. This allows SERV to be
used with single-port RAMs in most cases.
The reset_strategy parameter controls how much reset to apply to
SERV. It can be set to MINI for the default behaviour, or NONE to
only apply reset where absolutely needed and rely on POR to clear
FFs
