[POWERPC] spufs: Use computed sizes/#defines rather than literals in SPU coredump code

The spufs_coredump_reader array contains the size of the data that will be
returned by the read routine.  Currently these are specified as literals,
and though some are obvious, sizeof(u32) == 4, others are not, 69 * 8 ==  ???

Instead, use sizeof() whatever type is returned by each routine, or in
the case of spufs_mem_read() the #define LS_SIZE.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>