[POWERPC] spufs: Don't return -ENOSYS as extra notes size if spufs is not loaded

Because the SPU coredump code might be built as part of a module (spufs),
we have a stub which is called by the coredump code, this routine then calls
into spufs if it's loaded.

Unfortunately the stub returns -ENOSYS if spufs is not loaded, which is
interpreted by the coredump code as an extra note size of -38 bytes. This
leads to a corrupt core dump.

If spufs is not loaded there will be no SPU ELF notes to write, and so the
extra notes size will be == 0.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Acked-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>