orcarm: Fix flushing of icache when using dual map
On a codemem_dual_map setup, we need to flush the PROT_EXEC alias.
This seems to fix the crashing issues. The testsuite still fails a few tests, but those seem to be related to precision. The most significant digits all match.
Out of my depth on this, just kept poking a stick at it until it stopped poking back. Wish I'd thought to try this before spending a couple days trying to learn ARM/NEON assembly.