CVE-2017-5754

BugLink: http://bugs.launchpad.net/bugs/1742772

There's no reason to #error if we include ppc_asm.h in asm files, the
ifdef already prevents any problems.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>