include/linux/bug.h: fix sparse warning related to BUILD_BUG_ON_INVALID

Commit baf05aa9 ("bug: introduce BUILD_BUG_ON_INVALID() macro")
introduces this macro only when _CHECKER_ is not defined.  Define a
silent macro in the else condition to fix following sparse warning:

  mm/filemap.c:395:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  mm/filemap.c:396:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  mm/filemap.c:397:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  include/linux/mm.h:419:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  include/linux/mm.h:419:9: error: not a function <noident>
Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/bug.h

@@ -15,6 +15,7 @@ struct pt_regs;
 #define BUILD_BUG_ON_NOT_POWER_OF_2(n)
 #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(condition)
 #define BUILD_BUG() (0)
 #else /* __CHECKER__ */