[POWERPC] spufs: Write some SPU coredump values as ASCII

Unfortunately GDB expects some of the SPU coredump values to be identical
in format to what is found in spufs. This means we need to dump some of
the values as ASCII strings, not the actual values.

Because we don't know what the values will be, we always print the values
with the format "0x%.16lx", that way we know the result will be 19 bytes.

do_coredump_read() doesn't take a __user buffer, so remove the annotation,
and because we know that it's safe to just snprintf() directly to it.

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>