Use SimpleLoadField for JSObjectFieldAccessors, rather than compiling a new stub.

R=dslomov@chromium.org

Review URL: https://chromiumcodereview.appspot.com/76403002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17922 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
ARM: Optimize AccessArgumentsAt

Optimize register constraints and code generated for AccessArgumentsAt
Lithium instruction.

TEST=none
BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/78093004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17923 ce2b1a6d-e550-0410-aec6-3dcde31c8c00