kvm/svm: disable KCSAN for svm_vcpu_run()

For some reasons, running a simple qemu-kvm command with KCSAN will
reset AMD hosts. It turns out svm_vcpu_run() could not be instrumented.
Disable it for now.

 # /usr/libexec/qemu-kvm -name ubuntu-18.04-server-cloudimg -cpu host
	-smp 2 -m 2G -hda ubuntu-18.04-server-cloudimg.qcow2

=== console output ===
Kernel 5.6.0-next-20200408+ on an x86_64

hp-dl385g10-05 login:

<...host reset...>

HPE ProLiant System BIOS A40 v1.20 (03/09/2018)
(C) Copyright 1982-2018 Hewlett Packard Enterprise Development LP
Early system initialization, please wait...
Signed-off-by: Qian Cai <cai@lca.pw>
Message-Id: <20200415153709.1559-1-cai@lca.pw>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/svm.c

@@ -3344,7 +3344,7 @@ static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 
 void __svm_vcpu_run(unsigned long vmcb_pa, unsigned long *regs);
 
-static fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
+static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
 {
 	fastpath_t exit_fastpath;
 	struct vcpu_svm *svm = to_svm(vcpu);