KVM: nSVM: Unify RIP and PMU handling calls when emulating VMRUN

KVM: nSVM: Unify RIP and PMU handling calls when emulating VMRUN

The code paths for advancing RIP and retiring the instruction for RIP
are very similar whether or not caching vmcb12 succeeds. The only
difference is handling mapping failures (i.e. EFAULT).

Pull the mapping failure handling out and unify the calls to
svm_skip_emulated_instruction() and kvm_pmu_instruction_retired(), but
return immediately after if copying and caching vmcb12 failed. A nice
side effect of this is that the FIXME comment is now above the only code
path calling svm_skip_emulated_instruction().

Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260527234711.4175166-4-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>