[PATCH] uml: add debug switch for skas mode

It doesn't do anything but emit a warning, but there's a user population
that's used to adding 'debug' to the UML command line in order to gdb it.
With skas0 mode, that's not necessary, but these users need some indication
that 'debug' doesn't do what they want.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>