PPC: Now that vector ics are established for load, keyed load and call ics, let's remove dead code behind the flag.

Port 323ced9e

R=mvstanton@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1132513007

Cr-Commit-Position: refs/heads/master@{#28431}