powerpc/powernv/memtrace: Let the arch hotunplug code flush cache

powerpc/powernv/memtrace: Let the arch hotunplug code flush cache

BugLink: http://bugs.launchpad.net/bugs/1772991
Don't do this via custom code, instead now that we have support in the
arch hotplug/hotunplug code, rely on those routines to do the right
thing.

The existing flush doesn't work because it uses ppc64_caches.l1d.size
instead of ppc64_caches.l1d.line_size.

Fixes: 9d5171a8f248 ("powerpc/powernv: Enable removal of memory for in memory tracing")
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Rashmica Gupta <rashmica.g@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit 7fd6641de28fe9b5bce0c38d2adee0a72a72619e)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>