selftests: timers: freq-step: fix compile error

Fix compile error due to ksft_exit_skip() update to take var_args.

freq-step.c: In function ‘init_test’:
freq-step.c:234:3: error: too few arguments to function ‘ksft_exit_skip’
   ksft_exit_skip();
   ^~~~~~~~~~~~~~
In file included from freq-step.c:26:0:
../kselftest.h:167:19: note: declared here
 static inline int ksft_exit_skip(const char *msg, ...)
                   ^~~~~~~~~~~~~~
<builtin>: recipe for target 'freq-step' failed
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/timers/freq-step.c

@@ -229,10 +229,9 @@ static void init_test(void)
 	printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t",
 	       1e9 * precision);
 
-	if (precision > MAX_PRECISION) {
-		printf("[SKIP]\n");
-		ksft_exit_skip();
-	}
+	if (precision > MAX_PRECISION)
+		ksft_exit_skip("precision: %.0f ns > MAX_PRECISION: %.0f ns\n",
+				1e9 * precision, 1e9 * MAX_PRECISION);
 
 	printf("[OK]\n");
 	srand(ts.tv_sec ^ ts.tv_nsec);