KVM: SVM: clean up nested_svm_exit_handled_msr

This patch changes nested svm to call nested_svm_exit_handled_msr
directly and not through nested_svm_do.

[alex: fix oops due to nested kmap_atomics]

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>