Small cleanups in artInvokeInterfaceTrampoline

- No need to do a conflict table lookup when the passed method is
  already the interface method.
- Remove obsolete test that the IMT entry is indeed a conflict entry.
- Only call QuickArgumentVisitor::GetCallingMethod when needed.

Test: test.py
Bug: 112676029
Change-Id: I2d5da474ba3e8e4ad559fc7c13a19b04f4c2a515
3 files changed