KVM: SVM: fix error return code in svm_create_vcpu()

Fix to return a negative error code from the error handling case
instead of 0 in function svm_create_vcpu(), as done elsewhere in this
function.

Fixes: f4c847a9 ("KVM: SVM: refactor msr permission bitmap allocation")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Message-Id: <20201117025426.167824-1-chenzhou10@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>