tools: gpio: fix %llu warning in gpio-watch.c

Some platforms, such as mips64, don't map __u64 to long long unsigned
int so using %llu produces a warning:

gpio-watch.c: In function ‘main’:
gpio-watch.c:89:30: warning: format ‘%llu’ expects argument of type ‘long long unsigned int’, but argument 4 has type ‘__u64’ {aka ‘long unsigned int’} [-Wformat=]
89 | printf("line %u: %s at %llu\n",
| ~~~^
| |
| long long unsigned int
| %lu
90 | chg.info.offset, event, chg.timestamp_ns);
| ~~~~~~~~~~~~~~~~
| |
| __u64 {aka long unsigned int}

Replace the %llu with PRIu64 and cast the argument to uint64_t.

Fixes: 33f0c47b8fb4 ("tools: gpio: implement gpio-watch")
Signed-off-by: Kent Gibson <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

tools/gpio/gpio-watch.c

···
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <inttypes.h>
 #include <linux/gpio.h>
 #include <poll.h>
 #include <stdbool.h>
···
 				return EXIT_FAILURE;
 			}
 
-			printf("line %u: %s at %llu\n",
-			       chg.info.offset, event, chg.timestamp_ns);
+			printf("line %u: %s at %" PRIu64 "\n",
+			       chg.info.offset, event, (uint64_t)chg.timestamp_ns);
 		}
 	}