build_bug.h: remove BUILD_BUG_ON_NULL()

This macro is only used by net/ipv6/mcast.c, but there is no reason
why it must be BUILD_BUG_ON_NULL().

Replace it with BUILD_BUG_ON_ZERO(), and remove BUILD_BUG_ON_NULL()
definition from <linux/build_bug.h>.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Masahiro Yamada <[e-mail]>
Cc: Ian Abbott <[e-mail]>
Cc: Masahiro Yamada <[e-mail]>
Cc: Hideaki YOSHIFUJI <[e-mail]>
Cc: Alexey Kuznetsov <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/build_bug.h

···
 #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
 #define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
 #define BUILD_BUG_ON_ZERO(e) (0)
-#define BUILD_BUG_ON_NULL(e) ((void *)0)
 #define BUILD_BUG_ON_INVALID(e) (0)
 #define BUILD_BUG_ON_MSG(cond, msg) (0)
 #define BUILD_BUG_ON(condition) (0)
···
  * aren't permitted).
  */
 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); }))
-#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:(-!!(e)); }))
 
 /*
  * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the

net/ipv6/mcast.c

···
 #include <net/ip6_checksum.h>
 
 /* Ensure that we have struct in6_addr aligned on 32bit word. */
-static void *__mld2_query_bugs[] __attribute__((__unused__)) = {
-	BUILD_BUG_ON_NULL(offsetof(struct mld2_query, mld2q_srcs) % 4),
-	BUILD_BUG_ON_NULL(offsetof(struct mld2_report, mld2r_grec) % 4),
-	BUILD_BUG_ON_NULL(offsetof(struct mld2_grec, grec_mca) % 4)
+static int __mld2_query_bugs[] __attribute__((__unused__)) = {
+	BUILD_BUG_ON_ZERO(offsetof(struct mld2_query, mld2q_srcs) % 4),
+	BUILD_BUG_ON_ZERO(offsetof(struct mld2_report, mld2r_grec) % 4),
+	BUILD_BUG_ON_ZERO(offsetof(struct mld2_grec, grec_mca) % 4)
 };
 
 static struct in6_addr mld2_all_mcr = MLD2_ALL_MCR_INIT;