x86, boot, kaslr: Fix nuisance warning on 32-bit builds

Building 32-bit threw a warning on kASLR enabled builds:

arch/x86/boot/compressed/aslr.c: In function ‘mem_avoid_overlap’:
arch/x86/boot/compressed/aslr.c:198:17: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
   avoid.start = (u64)ptr;
                 ^

This fixes the warning; unsigned long should have been used here.
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/20141001183632.GA11431@www.outflux.netSigned-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/boot/compressed/aslr.c

@@ -195,7 +195,7 @@ static bool mem_avoid_overlap(struct mem_vector *img)
 	while (ptr) {
 		struct mem_vector avoid;
 
-		avoid.start = (u64)ptr;
+		avoid.start = (unsigned long)ptr;
 		avoid.size = sizeof(*ptr) + ptr->len;
 
 		if (mem_overlaps(img, &avoid))