powerpc/spufs: remove orphan declarations from spufs.h

Remove the following orphan declarations from spufs.h:
1. spufs_coredump_calls has been removed since
commit 48cad41f ("[POWERPC] spufs: Combine
spufs_coredump_calls with spufs_calls").

2. spufs_coredump_num_notes has been removed since
commit 936d5bf1 ("[POWERPC] spufs: Get rid of spufs_coredump_num_notes,
it's not needed if we NULL terminate").

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220913075029.682327-3-cuigaosheng1@huawei.com