Switch-interpreter: Make the instruction field constant.

The field is always set to the currently handled instruction.

The 'next' field stores the instruction to be executed next,
which defaults to fallthrough unless overwritten by handler.

Test: test.py -b -r --host --64 --interpreter
Test: run-libjdwp-tests.sh --mode=host --variant=X64 --debug --no-jit
Change-Id: Iadae51ead3e2f657717f190d07b04f4c28890f43
1 file changed