linux-ramdump-parser-v2: cleanup output of tracing

When tracing with read_physical, the result of what was read is printed.
The result may contain unprintable characters which wreak havok on
terminals. re-use the cleanupString function which is already in use
in several places to make the output readable.

Change-Id: I1a62c88f1d51038ba2c429d8ec918c58d39af4bf