x86/paravirt: Move the Xen-only pv_mmu_ops under the PARAVIRT_XXL umbrella

x86/paravirt: Move the Xen-only pv_mmu_ops under the PARAVIRT_XXL umbrella

Most of the paravirt ops defined in pv_mmu_ops are for Xen PV guests
only. Define them only if CONFIG_PARAVIRT_XXL is set.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel@lists.xenproject.org
Cc: virtualization@lists.linux-foundation.org
Cc: akataria@vmware.com
Cc: rusty@rustcorp.com.au
Cc: boris.ostrovsky@oracle.com
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/20180828074026.820-15-jgross@suse.com