Do not emit stack maps for runtime calls to ReadBarrierMarkRegX.

* Boot image code size variation on Nexus 5X
  (aosp_bullhead-userdebug build):
  - total ARM64 framework Oat files size change:
    115584120 bytes -> 109124728 bytes (-5.59%)
  - total ARM framework Oat files size change:
    97387728 bytes -> 92517584 (-5.00%)

Test: ART host and target (ARM, ARM64) tests.
Bug: 29506760
Bug: 12687968
Change-Id: I979d9fb2b4e09f4c0c7bf33af2cd91750a67f989