selftests/mqueue: fix 5 warnings about signed/unsigned mismatches

When building with clang, via:

make LLVM=1 -C tools/testing/selftest

...clang warns about several cases of using a signed integer for the
priority argument to mq_receive(3), which expects an unsigned int.

Fix this by declaring the type as unsigned int in all cases.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: John Hubbard <[e-mail]>
Reviewed-by: Muhammad Usama Anjum <[e-mail]>
Reviewed-by: Ryan Roberts <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Muhammad Usama Anjum <[e-mail]>
Cc: SeongJae Park <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Cc: Valentin Obst <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/testing/selftests/mqueue/mq_perf_tests.c

···
 void *cont_thread(void *arg)
 {
 	char buff[MSG_SIZE];
-	int i, priority;
+	int i;
+	unsigned int priority;
 
 	for (i = 0; i < num_cpus_to_pin; i++)
 		if (cpu_threads[i] == pthread_self())
···
 void *perf_test_thread(void *arg)
 {
 	char buff[MSG_SIZE];
-	int prio_out, prio_in;
+	int prio_out;
+	unsigned int prio_in;
 	int i;
 	clockid_t clock;
 	pthread_t *t;