Define VMALLOC_END as an unsigned long to match expected type.
Eliminates a warning:

arch/arm/mm/init.c: In function 'mem_init':
arch/arm/mm/init.c:606: warning: format '%08lx' expects type
   'long unsigned int', but argument 12 has type 'unsigned int'
Signed-off-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Daniel Walker <dwalker@codeaurora.org>