arch_ptrace() was modified to reference init_fpu() to fix up xstate
initialization, which overlooked the fact that there are configurations
that don't enable any of hard FPU support or emulation, resulting in
build errors on DSP parts.

Given that init_fpu() simply sets up the xstate slab cache and is
side-stepped entirely for the DSP case, we can simply always build in the
helper and fix up the references.
Reported-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: stable@kernel.org
Signed-off-by: Paul Mundt <lethal@linux-sh.org>