Fix non-blocking assignment in mem_lib.sv
Fix non-blocking assignment in mem_lib.sv

A typo in mem_lib.sv caused suboptimal mapping which led to high
resource usage on FPGA targets.

chipsalliance/Cores-SweRV-EL2,chipsalliance/Cores-SweRV-EL2,chipsalliance/Cores-SweRV-EL2,chipsalliance/Cores-SweRV-EL2