[turbofan] remove some of the dependency of Instruction on Schedule

R=bmeurer@chromium.org

BUG=

Review URL: https://codereview.chromium.org/646393002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24584 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Add control input to LoadField.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/649183003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24588 ce2b1a6d-e550-0410-aec6-3dcde31c8c00