[PPC64] xmon sparse cleanups

[Paul Mackerras]

David Gibson writes:

> This patch removes many sparse warnings from the xmon code.  Mostly
> K&R function declarations and 0-instead-of-NULLs.  There are still a
> whole bunch of warnings in xmon/ppc-opc.c, which is a copy of a file
> from binutils.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Acked-by: Paul Mackerras <paulus at samba.org>