kbuild: include limits.h in sumversion.c for PATH_MAX

POSIX says limits.h defines PATH_MAX so we should include it (which fixes
compiling on some systems like OS X).

Signed-off-by: Mike Frysinger <[e-mail]>
Signed-off-by: Sam Ravnborg <[e-mail]>

scripts/mod/sumversion.c

···
 #include <ctype.h>
 #include <errno.h>
 #include <string.h>
+#include <limits.h>
 #include "modpost.h"
 
 /*