doc/oops-tracing: add Code: decode info

Add info that the Code: bytes line contains <xy> or (wxyz) in some
architecture oops reports and what that means.

Add a script by Andi Kleen that reads the Code: line from an Oops report
file and generates assembly code from the hex bytes.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>