With GCC 4.5.1 we get the following warning: 

CC      arch/arm/mm/alignment.o
	arch/arm/mm/alignment.c: In function 'do_alignment':
	arch/arm/mm/alignment.c:720:21: warning: 'offset.un' may be used
	uninitialized in this function

This warning is triggered for the LDM/STM instructions which don't have
a register offset so set the offset to 0 to keep GCC happy.