KVM: VMX: Fix KVM_SET_SREGS with big real mode segments

KVM: VMX: Fix KVM_SET_SREGS with big real mode segments

(cherry picked from commit b246dd5df139501b974bd6b28f7815e53b3a792f)

For example migration between Westmere and Nehelem hosts, caught in big real mode.

The code that fixes the segments for real mode guest was moved from enter_rmode
to vmx_set_segments. enter_rmode calls vmx_set_segments for each segment.

Signed-off-by: Orit Wasserman <owasserm@rehdat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>