opt_mem_feedback - convert memory read-to-write port feedback paths to write enables

yosys> help opt_mem_feedback
opt_mem_feedback [selection]
This pass detects cases where an asynchronous read port is only connected via
a mux tree to a write port with the same address.  When such a connection is
found, it is replaced with a new condition on an enable signal, allowing
for removal of the read port.