media: cec-gpio: handle gpiod_get_value errors correctly

gpiod_get_value() can return negative values if an error occurs.
In several places this error code was ignored.

Ensure that errors codes are handled correctly throughout the CEC
pin framework and CEC pin drivers.

The return code of the cec_pin_ops read() callback had to be changed
from 'bool' to 'int', which mean the prototype of that callback in the
sun4i drm driver also had to be changed.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>