Return error code -EINVAL rather than '0' when the combo devices are not
supported.

Fixes: fa71c605 ("Input: combine hil_kbd and hil_ptr drivers")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20210515030053.6824-1-thunder.leizhen@huawei.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>