remove the xen dracut module

The Xen module is unnecessary and it has been for a while.
Most Xen systems will not be using the module, even now, because
xen-detect is not installed by default on most Xen systems, and
dracut uses xen-detect to decide whether to include the module.

It also has some problems:

1) it does not try loading xen_platform_pci;

2) it loads modules unnecessarily; modules.alias is where all Xen support
should reside.  Assuming xenbus_probe_frontend and xen_platform_pci
are loaded so that Xen devices are probed, other modules are picked up
automatically thanks to aliases such as

    alias xen:vbd xen_blkfront

3) Even not-so-recent kernels (say 2.6.32) require the xen_platform_pci
and xenbus_probe_frontend modules even for non-paravirtualized guests.
60xen/module-setup.sh picks the module only for PV guests.

So, just require xenbus_probe_frontend to be builtin, and also
xen_platform_pci for fully-virtualized guests, and remove the module.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

modules.d/60xen/module-setup.sh

@@ -1,42 +0,0 @@
-#!/bin/bash
-# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
-# ex: ts=8 sw=4 sts=4 et filetype=sh
-
-check() {
-    # No Xen-detect? Boo!!
-    if ! hash xen-detect 2>/dev/null; then
-        [[ -d /usr/lib/xen-default ]] && \
-            hash -p /usr/lib/xen-default/bin/xen-detect xen-detect || return 1
-    fi
-
-    . $dracutfunctions
-    [[ $debug ]] && set -x
-
-    # Yes, we are under Xen PV env.
-    xen-detect | grep -q -v PV || return 0
-
-    return 1
-}
-
-depends() {
-    return 0
-}
-
-installkernel() {
-    local _i
-    for _i in \
-        xenbus_probe_frontend xen-pcifront \
-        xen-fbfront xen-kbdfront xen-blkfront xen-netfront \
-        ; do
-        modinfo -k $kernel $_i >/dev/null 2>&1 && instmods $_i
-    done
-
-}
-
-install() {
-    hash xen-detect 2>/dev/null || \
-        hash -p /usr/lib/xen-default/bin/xen-detect xen-detect
-    inst "$(hash -t xen-detect)" /sbin/xen-detect
-    inst_hook pre-udev 40 "$moddir/xen-pre-udev.sh"
-}
-

modules.d/60xen/xen-pre-udev.sh

@@ -1,13 +0,0 @@
-#!/bin/sh
-# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
-# ex: ts=8 sw=4 sts=4 et filetype=sh
-xen-detect
-RC=$?
-if [ "$RC" = "1" ] ; then
-    modprobe xenbus_probe_frontend
-    modprobe xen-kbdfront
-    modprobe xen-fbfront
-    modprobe xen-blkfront
-    modprobe xen-netfront
-    modprobe xen-pcifront
-fi