[lworld] RFR: 8264897: [lworld] C2: Use BarrierSetC2::obj_allocate to buffer inline type in PhaseMacroExpand::expand_mh_intrinsic_return

[Yi Yang]

Try to reuse existing BarrierSetC2::obj_allocate functionality for PhaseMacroExpand::expand_mh_intrinsic_return.

Testing: x86_64 + linux+ slowdebug/release
[x] test/hotspot/jtreg/runtime/valhalla 
[x] test/hotspot/jtreg/compiler/valhalla 

Thanks!
Yang

-------------

Commit messages:
 - trailing whitespace
 - reuse obj_allocate PhaseMacroExpand::expand_mh_intrinsic_return

Changes: https://git.openjdk.java.net/valhalla/pull/385/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=385&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264897
  Stats: 104 lines in 1 file changed: 26 ins; 43 del; 35 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/385.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/385/head:pull/385

PR: https://git.openjdk.java.net/valhalla/pull/385