Drivers: hv: restore hypervcall page cleanup before kexec

Drivers: hv: restore hypervcall page cleanup before kexec

BugLink: http://bugs.launchpad.net/bugs/1676635
We need to cleanup the hypercall page before doing kexec/kdump or the new
kernel may crash if it tries to use it. Reuse the now-empty hv_cleanup
function renaming it to hyperv_cleanup and moving to the arch specific
code.

Fixes: 8730046c1498 ("Drivers: hv vmbus: Move Hypercall page setup out of common code")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit d6f3609d2b4c6d0eec01f398cb685e50da3e6013)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>