KVM x86 fixes for 6.4
- Fix a memslot lookup bug in the NX recovery thread that could
theoretically let userspace bypass the NX hugepage mitigation
- Fix a s/BLOCKING/PENDING bug in SVM's vNMI support
- Account exit stats for fastpath VM-Exits that never leave the super
tight run-loop
- Fix an out-of-bounds bug in the optimized APIC map code, and add a
regression test for the race.