Failed memory transactions should raise exceptions 14 (for fetch) or 15
(for load/store) with XEA2.
Memory accesses that result in TLB miss followed by an attempt to load
PTE from physical memory which fails should raise InstTLBMiss or
LoadStoreTLBMiss with XEA2.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>