KVM: x86: Account fastpath-only VM-Exits in vCPU stats

Increment vcpu->stat.exits when handling a fastpath VM-Exit without
going through any part of the "slow" path.  Not bumping the exits stat
can result in wildly misleading exit counts, e.g. if the primary reason
the guest is exiting is to program the TSC deadline timer.

Fixes: 404d5d7b ("KVM: X86: Introduce more exit_fastpath_completion enum values")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230602011920.787844-2-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>