KVM: SVM: make iopm_base static

Fixes sparse warning as well.
arch/x86/kvm/svm.c:69:15: warning: symbol 'iopm_base' was not declared. Should it be static?

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>