ARM: Shorter fast-path for read barrier field load.

Reduces the aosp_hammerhead-userdebug boot.oat by 2.2MiB,
i.e. ~2.2%, in the ART_USE_READ_BARRIER=true configuration.

Test: Tested with ART_USE_READ_BARRIER=true on Nexus 5.
Bug: 29966877
Bug: 12687968
Change-Id: I4454150003e12a1aa7f0cf451627dc1ee9a495ae
2 files changed