X86: Replace VarHandle.get() return type check with CheckCast node

This commit removes the varType check against the callsite return type.
The check is done after by an added HCheckCast node.

Test: art/test.py --host --32 -r -t 712-varhandle-invocations
Bug: 65872996
Change-Id: If4d966e0087da28349390474188e10dfb6f63832
5 files changed