Doc: networking: txtimestamp: fix printf format warning

Documentation/networking/timestamping/txtimestamp.c: In function ‘__print_timestamp’:
Documentation/networking/timestamping/txtimestamp.c:99:3: warning: format ‘%ld’ expects argument of type ‘long int’, but argument 3 has type ‘int64_t’ [-Wformat=]
fprintf(stderr, " (%+ld us)", cur_ms - prev_ms);

int64_t differs per platform, so a type specifier that differs along
with it is required.

Signed-off-by: Frans Klaver <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/networking/timestamping/txtimestamp.c

···
 #include <asm/types.h>
 #include <error.h>
 #include <errno.h>
+#include <inttypes.h>
 #include <linux/errqueue.h>
 #include <linux/if_ether.h>
 #include <linux/net_tstamp.h>
···
 #include <poll.h>
 #include <stdarg.h>
 #include <stdbool.h>
-#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
···
 		prev_ms = (long) ts_prev.tv_sec * 1000 * 1000;
 		prev_ms += ts_prev.tv_nsec / 1000;
 
-		fprintf(stderr, "  (%+ld us)", cur_ms - prev_ms);
+		fprintf(stderr, "  (%+" PRId64 " us)", cur_ms - prev_ms);
 	}
 
 	ts_prev = *cur;