selftests: cachestat: use proper syscall number macro

At the moment the cachestat syscall number is hard coded into the test
source code.
Remove that and replace it with the proper __NR_cachestat macro.
That ensures compatibility should other architectures pick a different
number.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/cachestat/test_cachestat.c

@@ -19,7 +19,6 @@ static const char * const dev_files[] = {
 	"/dev/zero", "/dev/null", "/dev/urandom",
 	"/proc/version", "/proc"
 };
-static const int cachestat_nr = 451;
 
 void print_cachestat(struct cachestat *cs)
 {
@@ -126,7 +125,7 @@ bool test_cachestat(const char *filename, bool write_random, bool create,
 		}
 	}
 
-	syscall_ret = syscall(cachestat_nr, fd, &cs_range, &cs, 0);
+	syscall_ret = syscall(__NR_cachestat, fd, &cs_range, &cs, 0);
 
 	ksft_print_msg("Cachestat call returned %ld\n", syscall_ret);
 
@@ -152,7 +151,7 @@ bool test_cachestat(const char *filename, bool write_random, bool create,
 			ksft_print_msg("fsync fails.\n");
 			ret = false;
 		} else {
-			syscall_ret = syscall(cachestat_nr, fd, &cs_range, &cs, 0);
+			syscall_ret = syscall(__NR_cachestat, fd, &cs_range, &cs, 0);
 
 			ksft_print_msg("Cachestat call (after fsync) returned %ld\n",
 				syscall_ret);
@@ -213,7 +212,7 @@ bool test_cachestat_shmem(void)
 		goto close_fd;
 	}
 
-	syscall_ret = syscall(cachestat_nr, fd, &cs_range, &cs, 0);
+	syscall_ret = syscall(__NR_cachestat, fd, &cs_range, &cs, 0);
 
 	if (syscall_ret) {
 		ksft_print_msg("Cachestat returned non-zero.\n");