Silences following build warning:

arch/arm/mm/init.c: In function 'mem_init':
arch/arm/mm/init.c:644: warning: format '%08lx' expects type 'long
unsigned int', but argument 12 has type 'unsigned int'
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Colin Cross <ccross@google.com>