uuid: cleanup <uapi/linux/uuid.h>

Exported header doesn't use anything from <linux/string.h>,
it is <linux/uuid.h> which uses memcmp().

Link: http://lkml.kernel.org/r/20171225171121.GA22754@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/uuid.h

@@ -17,6 +17,7 @@
 #define _LINUX_UUID_H_
 
 #include <uapi/linux/uuid.h>
+#include <linux/string.h>
 
 #define UUID_SIZE 16
 

include/uapi/linux/uuid.h

@@ -19,7 +19,6 @@
 #define _UAPI_LINUX_UUID_H_
 
 #include <linux/types.h>
-#include <linux/string.h>
 
 typedef struct {
 	__u8 b[16];