BugLink: https://bugs.launchpad.net/bugs/1830176

commit ebcd1bfc upstream.

Implement the barrier_nospec as a isync;sync instruction sequence.
The implementation uses the infrastructure built for BOOK3S 64.
Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
[mpe: Add PPC_INST_ISYNC for backport]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[juergh: Adjusted context.]
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>