x86/svm: Intercept and terminate RDPRU with #UD

x86/svm: Intercept and terminate RDPRU with #UD

The RDPRU instruction isn't supported at all (and it is unclear how this can
ever be offered safely to guests).  However, a guest which ignores CPUID and
blindly executes RDPRU will find that it functions.

Use the intercept and terminate with #UD.  While at it, fold SKINIT into the
same "unconditionally disabled" path.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>