arch: Add support for invalidating TLBs when draining

arch: Add support for invalidating TLBs when draining

This patch adds support for the memInvalidate() drain method.  TLB
flushing is requested by calling the virtual flushAll() method on the
TLB.

Note: This patch renames invalidateAll() to flushAll() on x86 and
SPARC to make the interface consistent across all supported
architectures.