Drop MMapOpts.MappingIdentity reference in loader.mapSegment.
Drop MMapOpts.MappingIdentity reference in loader.mapSegment.

PiperOrigin-RevId: 200261995
Change-Id: I7e460b18ceab2c23096bdeb7416159d6e774aaf7

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor