ART: Change GenPCUseDefEncoding(), turn on Load Hoisting for ARM64

This defines the PC resource mask as empty, as the PC is not
accessible on ARM64.

Unify code paths with x86 in LoadStoreElimination and LoadHoisting.

Change-Id: Iea8b9e666f306c7a6ff52b6c5bf7e05b35346b2c
6 files changed