ZGC: LIR_OpZStoreBarrier::_info shadows LIR_Op::_info

In LIR_OpZStoreBarrier, SonarCloud reports:
 Field "_info" shadows a field of the same name in base class "LIR_Op".

Here:
 https://github.com/openjdk/jdk/blob/0ef03f122866f010ebf50683097e9b92e41cdaad/src/hotspot/share/gc/z/c1/zBarrierSetC1.cpp#L290

This is similar to JDK-8278141: we can use the superclass `_info` instead.