x86/domctl: remove XEN_DOMCTL_pin_mem_cacheattr

x86/domctl: remove XEN_DOMCTL_pin_mem_cacheattr

Remove the implementation of XEN_DOMCTL_pin_mem_cacheattr since it has
been replaced by a dmop. Change xc_domain_pin_memory_cacheattr() so
that it is only defined when XC_WANT_COMPAT_DEVICEMODEL_API is set and
have it call the new dmop.  Leave the definitions of
XEN_DOMCTL_MEM_CACHEATTR_* since they are still used by QEMU.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>