dx: Fix result information on invoke-{polymorphic,custom}

Changes the annotation on invoke-custom and invoke-polymorphic
instructions to signify no result generated. This was problematic for
methods using lots of registers and led to missing move instructions
ahead of the invoke.

Test: dalvik/dx/tests/run-test 138
Bug: b/62722425

Change-Id: If8c02b7601cabf39272b862c89f6ecf1748f855a