platform/chrome: cros_typec_switch: Remove impossible condition

The type of 'index' is unsigned long long, which can't possibly be less
than zero. Remove the impossible check.

Cc: Prashant Malani <pmalani@chromium.org>
Cc: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220830225831.2362403-3-swboyd@chromium.org