test/py/tests/test_sleep.py: Add check for CONFIG_CMD_MISC

We can only run this command if the sleep command is enabled and that
depends on CONFIG_CMD_MISC

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/test/py/tests/test_sleep.py b/test/py/tests/test_sleep.py
index 5c1a262..b59a4cf 100644
--- a/test/py/tests/test_sleep.py
+++ b/test/py/tests/test_sleep.py
@@ -9,6 +9,8 @@
     """Test the sleep command, and validate that it sleeps for approximately
     the correct amount of time."""
 
+    if u_boot_console.config.buildconfig.get('config_cmd_misc', 'n') != 'y':
+        pytest.skip('sleep command not supported')
     # 3s isn't too long, but is enough to cross a few second boundaries.
     sleep_time = 3
     tstart = time.time()