RFR[T]: 8240246: Avoid cast_to_oop from char*

[Kim Barrett]

Please review this trivial change of a cast_to_oop argument from char*
to address.  This removes the only call of that function with a char*
argument.

CR:
https://bugs.openjdk.java.net/browse/JDK-8240246

Webrev:
https://cr.openjdk.java.net/~kbarrett/8240246/open.00/

Testing:
mach5 tier1