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>
diff --git a/cmd/legacy_led.c b/cmd/legacy_led.c
index 50de7e8..db312ae 100644
--- a/cmd/legacy_led.c
+++ b/cmd/legacy_led.c
@@ -12,6 +12,7 @@
 #include <command.h>
 #include <status_led.h>
 #include <vsprintf.h>
+#include <linux/string.h>
 
 struct led_tbl_s {
 	char		*string;	/* String for use in the command */