restore: Reserve space in restorer for FPU frame

For code simplicity we reserve the maximum size which
might be needed to form an FPU frame (ie for both
xsave and fxsave operations).

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>