configs, dev, learning-gem5, python, tests: more clarification

This commit contains the rest of the base 2 vs base 10 cache/memory
size clarifications. It also changes the warning message to use
warn(). With these changes, the warning message should now no
longer show up during a fresh compilation of gem5.

Change-Id: Ia63f841bdf045b76473437f41548fab27dc19631

configs/example/gem5_library/dramsys/dramsys-traffic.py

@@ -40,12 +40,12 @@ from gem5.simulate.simulator import Simulator
 memory = DRAMSysMem(
     configuration="ext/dramsys/DRAMSys/configs/ddr4-example.json",
     recordable=True,
-    size="4GB",
+    size="4GiB",
 )
 
 generator = LinearGenerator(
     duration="250us",
-    rate="40GB/s",
+    rate="40GiB/s",
     num_cores=1,
     max_addr=memory.get_size(),
 )