platform/chrome: cros_ec_typec: Check for device within remove function

In a couple of call sites, we use the same pattern of checking for a
partner or cable device before attempting to remove it. Simplify this by
moving those checks into the remove functions.

Cc: Benson Leung <bleung@chromium.org>
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20210319015103.3751672-1-pmalani@chromium.org