tools/libxc: Remove xsave calculations from libxc

tools/libxc: Remove xsave calculations from libxc

libxc performs a lot of calculations for the xstate leaf when generating a
guests cpuid policy.  To correctly construct a policy for an HVM guest, this
logic depends on native cpuid leaking through from real hardware.

In particular, the logic is potentially wrong for an HVM-based toolstack
domain (e.g. PVH dom0), and definitely wrong if cpuid faulting is applied to a
PV domain.

Xen now performs all the necessary calculations, using native values.  The
only piece of information the toolstack need worry about is single xstate
feature leaf.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>