[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/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 5ad149b..ff16063 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -98,6 +98,15 @@
 	  xmon is normally disabled unless booted with 'xmon=on'.
 	  Use 'xmon=off' to disable xmon init during runtime.
 
+config XMON_DISASSEMBLY
+	bool "Include disassembly support in xmon"
+	depends on XMON
+	default y
+	help
+	  Include support for disassembling in xmon. You probably want
+	  to say Y here, unless you're building for a memory-constrained
+	  system.
+
 config IRQSTACKS
 	bool "Use separate kernel stacks when processing interrupts"
 	depends on PPC64