arch/x86/kernel/e820.c: quiet sparse noise about plain integer as NULL pointer

The last parameter to sort() is a pointer to the function used
to swap items.  This parameter should be NULL, not 0, when not
used.  This quiets the following sparse warning:

 warning: Using plain integer as NULL pointer

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: hartleys@visionengravers.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/e820.c

@@ -296,7 +296,7 @@ int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
 	chg_nr = chgidx;
 
 	/* sort change-point list by memory addresses (low -> high) */
-	sort(change_point, chg_nr, sizeof *change_point, cpcompare, 0);
+	sort(change_point, chg_nr, sizeof *change_point, cpcompare, NULL);
 
 	/* create a new bios memory map, removing overlaps */
 	overlap_entries = 0;	 /* number of entries in the overlap table */