Revert^4 "ART: Dual mapping of JIT code pages"

This reverts commit 1bfce389.

This change adds a fix for stale data in the JIT code cache when dual
mappings of the code cache are employed. With dual mappings, newly
compiled code is written into the non-executable mapping of the code
cache. An additional data cache flush is needed to ensure the new
code is written out to the point of unification in the memory
hierarchy.

Test: manual
Bug: 66095511
Bug: 116761923

Change-Id: Ib5fa83f22ee4fee1d0f80e16b974e1677c20af9b