Input: zinitix - don't fail if linux,keycodes prop is absent

Input: zinitix - don't fail if linux,keycodes prop is absent

When initially adding the touchkey support, a mistake was made in the
property parsing code. The possible negative errno from
device_property_count_u32() was never checked, which was an oversight
left from converting to it from the of_property as part of the review
fixes.

Re-add the correct handling of the absent property, in which case zero
touchkeys should be assumed, which would disable the feature.

Reported-by: Jakob Hauser <jahau@rocketmail.com>
Tested-by: Jakob Hauser <jahau@rocketmail.com>
Fixes: 075d9b22c8fe ("Input: zinitix - add touchkey support")
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Nikita Travkin <nikita@trvn.ru>
Tested-by: Yassine Oudjana <y.oudjana@protonmail.com>
Link: https://lore.kernel.org/r/20241004-zinitix-no-keycodes-v2-1-876dc9fea4b6@trvn.ru
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>