ARM: compile fix for DEBUG_LL=y && MMU=n

debug_ll_addr is only used on machines with an MMU so it can be #ifdef'ed
out safely. This fixes:

arch/arm/kernel/debug.S: Assembler messages:
arch/arm/kernel/debug.S:104: Error: too many positional arguments

The problem was introduced in e5c5f2a ARM: implement debug_ll_io_init().

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Olof Johansson <olof@lixom.net>