Add xsave/xrstor support for LWP Because LWP is not tracked by TS, which is used in current xsave/xrstor implementation for FPU/AVX. As a result, we have to save and restore LWP in extended area whenever vcpu is re-scheduled. To avoid unnecessary lwp save/restore, this patch checks the LWP_CBADDR to determine whether LWP has been turned on. Signed-off-by: Wei Huang