includecheck fix for kernel/params.c

Fix the following 'make includecheck' warning:
  kernel/params.c: linux/string.h is included more than once.
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/params.c

@@ -24,7 +24,6 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/ctype.h>
-#include <linux/string.h>
 
 #if 0
 #define DEBUGP printk