KVM: SVM: align shadow CR4.MCE with host

This patch aligns the host version of the CR4.MCE bit with the CR4 active in
the guest. This is necessary to get MCE exceptions when the guest is running.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>