[POWERPC] Make xmon disassembly optional

While adding spu disassembly support it struck me that we're actually
carrying quite a lot of code around, just to do disassembly in the case
of a crash.

While on large systems it's not an issue, on smaller ones it might be
nice to have xmon - but without the weight of the disassembly support.
For a Cell build this saves ~230KB (!), and for pSeries ~195KB.

We still support the 'di' and 'sdi' commands, however they just dump
the instruction in hex.

Move the definitions into a header to clean xmon.c just a tiny bit.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
diff --git a/arch/powerpc/xmon/ppc-dis.c b/arch/powerpc/xmon/ppc-dis.c
index 3b67bee..0865274 100644
--- a/arch/powerpc/xmon/ppc-dis.c
+++ b/arch/powerpc/xmon/ppc-dis.c
@@ -21,8 +21,7 @@
 #include "nonstdio.h"
 #include "ansidecl.h"
 #include "ppc.h"
-
-extern void print_address (unsigned long memaddr);
+#include "dis-asm.h"
 
 /* Print a PowerPC or POWER instruction.  */