test: Fix skip check for sleep command test

When the config option CMD_MISC was renamed to CMD_SLEEP the check
in the test for the sleep command was not updated. Do that now.

Fixes: 16060854095 ("cmd: Rename CMD_MISC to CMD_SLEEP")
Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed