Commit 40df2d1d "[ARM] Update Xscale and Xscale3 PTE mappings" was
fingered by git-bisect for a boot failure on iop13xx. The change made
L_PTE_MT_WRITETHROUGH mappings L2-uncacheable. Russell points out that
this mapping is used for the vector page. Given the regression, and the
fact this page is used often, restore the old behaviour.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>