Documentation: Add nospectre_v1 parameter

commit 26cb1f36c43ee6e89d2a9f48a5a7500d5248f836 upstream.

Currently only supported on powerpc.

Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>