global: Add <linux/string.h> instead of long indirect include path

In a number of cases we have C files which rely on a chain of indirect
include paths to get <linux/string.h> to be included via <command.h>. To
facilitate cleaning up <command.h> make this code directly include
<linux/string.h>.

Signed-off-by: Tom Rini <trini@konsulko.com>

cmd/stackprot_test.c

@@ -4,6 +4,7 @@
  */
 
 #include <command.h>
+#include <linux/string.h>
 
 static int do_test_stackprot_fail(struct cmd_tbl *cmdtp, int flag, int argc,
 				  char *const argv[])