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/optee.c b/cmd/optee.c
index e3aae5e..155c9f1 100644
--- a/cmd/optee.c
+++ b/cmd/optee.c
@@ -6,6 +6,7 @@
 #include <errno.h>
 #include <tee.h>
 #include <vsprintf.h>
+#include <linux/string.h>
 
 #define TA_HELLO_WORLD_CMD_INC_VALUE 0
 /* This needs to match the UUID of the Hello World TA. */